Why is desire the root of suffering?

the buddha says that chanda is bad because it is the source of what is like or disliked and what is liked and disliked is the source of ''jealousy and stinginess'' which are bad.

“Dear sir, what fetters bind the gods, humans, demons, dragons, fairies—and any of the other diverse creatures—so that, though they wish to be free of enmity, violence, hostility, and hate, they still have enmity, violence, hostility, and hate?” Such was Sakka’s question to the Buddha. And the Buddha answered him:

“Lord of gods, the fetters of jealousy and stinginess bind the gods, humans, demons, dragons, fairies—and any of the other diverse creatures—so that, though they wish to be free of enmity, violence, hostility, and hate, they still have enmity, violence, hostility, and hate.” Such was the Buddha’s answer to Sakka. Delighted, Sakka approved and agreed with what the Buddha said, saying:

“That’s so true, Blessed One! That’s so true, Holy One! Hearing the Buddha’s answer, I’ve gone beyond doubt and got rid of indecision.”

And then, having approved and agreed with what the Buddha said, Sakka asked another question:

“But dear sir, what is the source, origin, birthplace, and inception of jealousy and stinginess? When what exists is there jealousy and stinginess? When what doesn’t exist is there no jealousy and stinginess?”

“The liked and the disliked, lord of gods, are the source of jealousy and stinginess. When the liked and the disliked exist there is jealousy and stinginess. When the liked and the disliked don’t exist there is no jealousy and stinginess.”

“But dear sir, what is the source of what is liked and disliked?” “Desire is the source of what is liked and disliked.”

“But what is the source of desire?” “Thought is the source of desire.”

“But what is the source of thought?” “Concepts of identity that emerge from the proliferation of perceptions are the source of thoughts.”

https://suttacentral.net/dn21/en/sujato

Seems like you are referring to the 2nd Noble Truth:

"And what is the noble truth of the origin of suffering?"

"It’s the craving that leads to future rebirth, mixed up with relishing and greed, looking for enjoyment in various different realms." (MN 141)

Here the word "taṇhā" is translated as craving but it's not the same as desire.

From my personal observations and experiences I've concluded that painful feelings are the cause of suffering some what similarly to dependent origination:

"Feeling is a condition for craving."

vedanāpaccayā taṇhā; (SN 12.1)

Painful feelings are not really the same as desire but can be associated.

Anything that causes painful feelings causes suffering but if someone were to have wishes or desires that causes pleasant feelings or leads towards arahantship it would be beneficial.

Right Effort is part of the Noble Eightfold Path and requires desire and energy in the right direction:

“And what, bhikkhus, is right effort? Here, bhikkhus, a bhikkhu generates desire for the nonarising of unarisen evil unwholesome states; he makes an effort, arouses energy, applies his mind, and strives. He generates desire for the abandoning of arisen evil unwholesome states…. He generates desire for the arising of unarisen wholesome states…. He generates desire for the maintenance of arisen wholesome states, for their nondecay, increase, expansion, and fulfilment by development; he makes an effort, arouses energy, applies his mind, and strives. This is called right effort." (SN 45.8)

The Eigthfold Path is the path towards ending suffering.

It is also mentioned that iddhi development is required for achieving arahantship, which requires desire as well:

“Mendicants, all the mendicants in the past … future … present who realize the undefiled freedom of heart and freedom by wisdom in this very life, and who live having realized it with their own insight due to the ending of defilements, do so by developing and cultivating the four bases of iddhi power." (SN 51.7)

The four bases of iddhi is defined as developing concentration founded on desire, persistence, intent, and discrimination.

The purpose in Buddhism is to achieve arahantship or enlightenment which is the highest happiness the most extreme pleasantness...and desire is required to achieve this.

Arahantship is defined as āsavakkhaya or ending of asavas.

Asavas is translated usually as "mental fermentations", "defilements", "cankers", "taints" but never as desire.

So we see the suttas supporting the idea that painful feelings and asavas could also be called the root of suffering rather than craving.

It seems to me like many modern day Buddhists have become similar to the ascetics who Gautama criticized...the ascetic practices austerities, refrains from sensual pleasures, and follows some of the same rules as modern day Buddhists but the ascetic almost never goes to heaven or any pleasant destination after death because their practices yield painful feelings.

"And what is the way of taking up practices that is painful now and results in future pain?...And so they live committed to practicing these various ways of mortifying and tormenting the body. When their body breaks up, after death, they’re reborn in a place of loss, a bad place, the underworld, hell. This is called the way of taking up practices that is painful now and results in future pain." (MN 45)

If someone were to merely give up on desire without generating pleasant feelings or good kamma or entering into higher states like the jhanas or developing the six higher knowledges they would probably become pretty similar to the ascetic producing painful feelings and not achieving arahantship.

It is also mentioned in MN 71 that only 1 ascetic in the past 91 eons went to heaven whereas many lay people do go to heaven so many of the lay peoples' practices are better than the ascetic's.

It also seems to me like there might be not any real arahants well-developed in the six higher knowledges that exist anymore because if they did they could easily explain the true purpose and see that Gautama was actually telling people to avoid things that causes painful feelings and embrace things that leads towards pleasant feelings...it was for the welfare and happiness of beings.

I've heard for instance some people that claim that the higher states aren't actually pleasant, how ridiculous!

If the world is empty of arahants or beings somewhat close to arahantship then the dhamma is lost! People can interpret words in any way without words assisting in achieving arahantship words don't really have any value.

Social help for needy, poor and depressed is always worthy. But still the who helping do not know the root cause of pain. Buddha was requested by King Bimbisara to abandon the search, instead make service to their fellow being and be happy. But Buddha said, the root of suffering is deep. Even the path of service is temporary happiness and also last in conflict. There is subtle cause in each living being that who don't give up, are bound by law of karma to become again. Pulling out the very root is called as total remedy. But while doing so if he doing this great deeds for welfare for others, Buddha has no objection? It's your duty.

I have this doubt also. But when I have this question in mind, I learned the another teaching of Buddha, which is, - choose the 'Madhya Marga'(take the middle path) - It gave me the answer to my firs question. Being moderate in anything and everything in your life, helps you a lot. Desire is good thing, it gives a purpose to reach a goal but greed is bad, it brings you pain only.

It isn't an enemy but very required. Seeing that desire is, out of not-knowing, the cause of suffering, one needs a lot of desire to get ride of it.

Isn't desire for sensuality, becoming, not-becoming the actual reason why people neither help themselves or others? How can someone full of desire help anyone?

Without desire nothing can be reached, but after having abound all desires there are no more limits in regard of help.

So maybe investigate what keeps you from really helping, being helpful.

(note that this is not given for trade, exchange, stacks or entertain ones desires toward this circle here, but for some desires to go on to leave it)

Buddhism is not understood with our mind, but with our experience. Do the meditation and other practices, and gradually over months, years, you will start to SEE the connection between your desire and your suffering.

Each Buddhist proves Buddhism to themselves through their practice and that is the only way to understand an experience.

The word "desire" is an English word. The Buddha did not speak English.

Buddhism teaches "tanha" is the root of suffering. "Tanha" is generally translated as "craving". It literally means "thirst". "Tanha" is uwnwholesome.

Therefore, in respect to meditation, the type of "wholesome or skilful desire" used in meditation is called "chanda iddhipada" or "samma-sankhappa".

As for the worldly materialistic examples in the question, you answered your own question, when you said: "Not everyone seeks nirvana".

The abandoning of tanha is for those who seek Nirvana. Therefore, what is the point of your question?

As for suffering, whenever it occurs, there is craving. Therefore, craving is the root of suffering.

If you crave to be a billionaire and you achieve this, obviously there is no suffering about becoming a billionaire.

But if you crave to be a billionaire and you do not achieve this, obviously there will be suffering about becoming a billionaire and this suffering is caused by the unfulfilled craving.

Or if you want your children to do good things but your children refuse, if you suffer about this, this is due to your "desire" or "craving". Therefore, even "good desires" can bring suffering.

In conclusion, whenever suffering arises, a cause of this suffering will be "craving" or "unwise desire". "Craving is the root of suffering". This is an irrefutable fact.

As the Buddha explains in numerous suttas, desire is the root of suffering because it sets the gears of becoming in motion.

Becoming is a process of gradually emerging (and supporting already emerged) sense of individual narrative, the story of "my" life. Once there's such story, there's a framework for judging experience as right or wrong, success or failure etc. Once there's judgement, there's suffering.

So, once there's desire, there's purposefull activity, once there's purposefull activity, there's food for the sense of I, once there's sense of I, there is comparison, once there's comparison there's suffering.

Working on your hobbies, advancing your career, growing a business, developing a family, nurturing a child, improving your health through good diet and exercise, going on vacations, increasing your wealth, using your money for the enjoyment or development of yourself and others, raising your status in the world, attaining fame in society etc. could all make you happy.

It would not just make you happy, but also your family and people around you. If you start a business, you might create jobs for others. If you buy goods and services, you sustain others' income.

All these types of worldly happiness definitely need sensual cravings (kama tanha) and cravings of becoming something (bhava tanha).

Buddhism teaches the pursuit of happiness and the elimination of suffering (dukkha). The short term happiness goal in Buddhism is worldly happiness, when it is achieved through virtue, merit, charity and harmony. Also see this answer to the excellent question "Can a Buddhist own and run a billion dollar business?".

Here's another example of a sutta where worldly happiness is preached in Buddhism. From AN 5.58:

He always does his duty toward his parents;
he promotes the welfare of his wife and children.
He takes care of the people in his home
and those who live in dependence on him.

The wise person, charitable and virtuous,
acts for the good of both kinds of relatives,
those who have passed away
and those still living in this world.

He benefits ascetics and brahmins,
and also the deities;
he is one who gives rise to joy
while living a righteous life at home.

Having done what is good,
he is worthy of veneration and praise.
They praise him here in this world
and after death he rejoices in heaven.

However, worldly happiness is a short term type of happiness. Nothing ever lasts.

Your health and youth would not last forever. Your loved ones or friends may forsake you. Your career or businesses may dwindle. Your money and possessions may get stolen. Your peaceful life in your country may be replaced by civil unrest.

No one knows this better than the Buddha, who was a prince who had everything. Realizing that worldly happiness would not last forever, he set out to find permanent happiness and eventually found it. To achieve permanent happiness, you must uproot craving.

There are three types of craving (tanha): craving for sensual pleasures, craving to become something (that makes someone have ambition) and the craving to not become something (that makes one suicidal or withdrawn).

If you crave for food, and eat some tasty food, you may cling to it or become attached to it. You think and fantasize about it even when it's not there. That's clinging or attachment. Craving gives rise to clinging and clinging gives rise to greed or lust to acquire it.

If someone prevents you from getting the tasty food that you cling to, then you feel angry. That hatred or aversion arises because you were denied what you cling to.

If this anger makes you enraged that you go and harm this person who prevents you from getting what you want, this is delusion. Delusion clouds your better judgment.

The craving to become something is similar. Examples are like wanting to get a gold medal or to get a promotion or to become doctor or professor or get recognition etc.

If you crave to get recognition and get it once, you may cling to it and want it even when it's not present. This leads you to do things to get recognition as you have greed (or lust) for it.

If you don't get recognition, but someone else does, you become envious. That's aversion.

If continuously not getting recognition leads you to become depressed, which clouds your normal healthy state of mind, then that's delusion.

That is how craving is the root of all suffering. When you uproot craving, you will uproot suffering.

Of course, it is not a MUST that you seek the permanent happiness of Nibbana. If you are only seeking the short term type of happiness, that is worldly happiness, make sure you include virtue, merit, charity and harmony. At the very minimum, the practice of the five precepts is needed.