The question of why do we have craving

In Buddhism everything boils down to we as humans and animals crave.

Yes.

Even in worldly affairs: Craving -> searching -> gain -> decision-making -> desire and lust -> attachment -> possessiveness -> stinginess -> safe-guarding -> various evils, unwholesome phenomena - Mahā,nidāna Sutta

Also the 12 link generic version of Dependent Arising: ... -> feeling -> Craving -> Clinging -> ...

So the question becomes why are we hard coded to crave.

Particularly craving arises when you get attached to the pleasant feeling. Pahāna Sutta

In context of Dependent Arising both craving and aversion are 2 sides of the same coin. The case of unpleasant and neutral feeling leading to aversion and ignorance is coved in the above Sutta. In this context craving [, aversion, ignorance] arises due to due to feelings which are pleasant, unpleasant, neutral.

Carving, aversion and ignorance are latent tendencies. They are reinforced due to our habitual reaction to sensation. That is why in meditation (as taught by some teachers at least), you are asked to be equanimous seeing the arising and passing of sensation.

Personally i think every living being is hard wired to crave because of survival. I think at a primal level for every living being the main objective is to survive and to reproduce and i think that is why we have craving and all those akusala karma such as jealously anger etc...

This is also true as the the cycle: Craving -> searching -> gain -> decision-making -> desire and lust -> attachment -> possessiveness -> stinginess -> safe-guarding -> various evils, unwholesome phenomena - Mahā,nidāna Sutta

Google for the "12 dependent arisings". All dependent arisings lead to sufferings and craving is one of the dependent arisings.

Buddha's teaching is able to cut one of the dependent arisings thus preventing subsequent arisings from taking place, leading to enlightenment..

There are various suttas which say there are three roots: delusion, craving, and aversion.

Also, ignorance is identified as the first of the 12 nidanas, and the root cause of dukkha.

I think that "right view" (or wisdom) might be an antonym of "ignorance": so seeing things properly, for example understanding the disadvantages of craving, is what eventually leads to dispassion, renunciation, the end of craving; and conversely, the opposite (i.e. ignorance, lack of right view, insufficient wisdom) could be called the root cause of craving.

Another theory is that craving is conditioned by feelings which are conditioned by sensations: so maybe these could be seen as the cause of craving (for which, I think the antidote is "guarding the sense-doors").

AN 3:76 Bhava Sutta: Becoming, gives us an analogy to describe how becoming is produced: “Kamma is the field, consciousness the seed, and craving the moisture.” Kamma gives us a range of possibilities in which the seed of consciousness can be planted and on which it can feed. Craving is the moisture that keeps the seed alive and allows it to grow into a state of becoming.

It is Kamma, rooted in ignorance and craving (Tanhā, thirst), that conditions rebirth. This life-stream flows ad infinitum, as long as it is fed by the muddy waters of ignorance and craving. When these two are completely cut off, then only, if one so wishes, does the stream cease to flow, rebirth ends as in the case of the Buddhas and Arahats. The most valuable evidence Buddhists cite in favor of rebirth is the Buddha, for He developed a knowledge which enabled Him to read past and future lives.

Thus the cause for the arising of suffering is craving. Craving results from delusion, which prevents man from seeing things as they really are. Therefore, cessation of suffering is achieved when craving is eradicated and extinguished. The path leading to the cessation of craving is the Noble Eightfold Path, expounded by the Enlightened One.

Just an Opinion

Craving: is like, "A Motion needs space" A stone or dead person can get rid of this. e.g Your craving saying let's ask about craving :) that means you are alive, you need this internally like body needs parts externally.

The Puttamansa Sutta lists four nutriments for the sustenance of beings (sattānaṃ) who have come to be (bhūtānaṃ) and for the support of beings seeking to be (sambhavesīnaṃ), namely:

1. Edible food, coarse and fine;
2. Sense-impression;
3. Volitional thought; and
4. Consciousness.

For unenlightened beings, craving is included within the nutriment of volitional thought, as stated:

If the nutriment volitional thought is comprehended, the three kinds of craving are thereby comprehended.

Puttamansa Sutta

Thus, at a primal level, for every unenlightened living being, craving serves the main objective (of nature) to survive and to reproduce.

As for the enlightened, they survive more skilfully relying on wisdom rather than craving.

The word 'dharma' means 'that which supports' thus craving also supports life but it is an 'akusala dhamma', namely, an unskilful means of support. For example, the suttas state:

Thus, Ānanda, in dependence upon feeling there is craving; in dependence upon craving there is pursuit; in dependence upon pursuit there is gain; in dependence upon gain there is decision-making; in dependence upon decision-making there is desire and lust; in dependence upon desire and lust there is attachment; in dependence upon attachment there is possessiveness; in dependence upon possessiveness there is stinginess; in dependence upon stinginess there is safeguarding; and because of safeguarding, various evil unwholesome phenomena originate—the taking up of clubs and weapons, conflicts, quarrels, and disputes, insulting speech, slander and falsehoods. Therefore, Ānanda, this craving is the cause, source, origin, and condition for those various evil unwholesome phenomena.

To add, "we" do not crave. To the contrary, it is craving that creates the idea of "we". To quote:

"Who, O Lord, craves?"

"The question is not correct," said the Exalted One. "I do not say that 'he craves.' Had I said so, then the question 'Who craves?' would be appropriate. But since I did not speak thus, the correct way to ask the question will be 'What is the condition of craving?' And to that the correct reply is: 'Feeling is the condition of craving and craving is the condition of clinging.'"

SN 12.12

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An uninstructed, run-of-the-mill person assumes form, feeling, perception, fabrication &/or conscious to be a self. That assumption is a fabrication. Now what is the cause, what is the origination, what is the birth, what is the coming-into-existence of that fabrication? To an uninstructed, run-of-the-mill person, touched by that which is felt born of contact with ignorance, craving arises. That fabrication [of self] is born of that.

SN 22.81