why can't we swap one desire for another and another?

MN 54 describes how sensual pleasures cannot bring satisfaction and the more than are indulged in the more they bring chronic weariness.

The more pleasures are indulged in, the more craving grows, the more the capacity to obtain pleasure from sensual pleasures diminishes.

This is why people become addicts and reach a point where their objects of addiction cease to bring pleasure and bring suffering.

Householder, suppose a dog, overcome by hunger and weakness, was waiting by a butcher’s shop. Then a skilled butcher or his apprentice would toss the dog a well hacked, clean hacked skeleton of meatless bones smeared with blood. What do you think, householder? Would that dog get rid of his hunger and weakness by gnawing such a well hacked, clean hacked skeleton of meatless bones smeared with blood?”

“No, venerable sir. Why is that? Because that was a skeleton of well hacked, clean hacked meatless bones smeared with blood. Eventually that dog would reap weariness and disappointment.”

“So too, householder, a noble disciple considers thus: ‘Sensual pleasures have been compared to a skeleton by the Blessed One; they provide much suffering and much despair, while the danger in them is great.’

'swap one impermanent source of satisfaction for another'

Is this not exactly what we do all our lives?

did the Buddha say any words on why we cannot?

Is the first noble truth not exactly why we musn't even if we can?

There is no 'cannot' there is only awakening to folly.

We can not replace A by B by C by D and so on because the consumer is perishable. The euphoria which gets generated by coming together of body and drugs fails to get generated after some time as the body dies or becomes deseased. This applies to all the objects of satisfaction. For example imagine someone changing wife every year to enjoy sex. But after some time his sexual organ will fail to respond to sexual stimuli as he will become diseased or will leave his body. Therefore objects of satisfaction can not be replaced forever.

For example, one might take drug A to induce euphoria, then when drug A wears off, replace it by drug B, and so on.

The problem with replacing a sensual object with another is that over time, the body system's sensual receptacles grow numb to the old stimuli and it'd require stronger and stronger stimuli to trigger the same level of pleasurable response. An analogy is when one drinks salt water to try to quench his thirst, it only makes his thirst more severe, and s/he'll keep drinking salt water to death.

But did the Buddha say any words on why we cannot swap one impermanent source of satisfaction for another, and continue doing so?

The Buddha did say about a gradual process of replacing one gross/coarse source of satisfaction with other less coarse/more refined ones, and incrementally more and more refined ones, until a day when one's defilements are completely eradicated and one no longer craves any kind of stimuli coarse or subtle at all:

Even though a disciple of the noble ones has clearly seen as it actually is with right discernment that sensuality is of much stress, much despair, & greater drawbacks, still — if he has not attained a rapture & pleasure apart from sensuality, apart from unskillful mental qualities, or something more peaceful than that[4] — he can be tempted by sensuality. But when he has clearly seen as it actually is with right discernment that sensuality is of much stress, much despair, & greater drawbacks, and he has attained a rapture & pleasure apart from sensuality, apart from unskillful mental qualities, or something more peaceful than that, he cannot be tempted by sensuality. ~~ MN 14 ~~

MN 75 gives the analogy of a leper and shows that by swapping one desire for another, we would simply be making our craving and attachments progressively worse, which is a slippery slope to deepening our suffering.

The reason for this is that sensual pleasures are impermanent, and either their future absence will cause suffering, or their future side effects will cause suffering. They can't be sustained forever. And when you swap one desire for another, craving gets deepened and the "sensual fever" burns deeper. This will result in suffering becoming deeper.

"Now suppose that there was a leper covered with sores & infections, devoured by worms, picking the scabs off the openings of his wounds with his nails, cauterizing his body over a pit of glowing embers. The more he cauterized his body over the pit of glowing embers, the more disgusting, foul-smelling, & putrid the openings of his wounds would become, and yet he would feel a modicum of enjoyment & satisfaction because of the itchiness of his wounds. In the same way, beings not free from passion for sensual pleasures — devoured by sensual craving, burning with sensual fever — indulge in sensual pleasures. The more they indulge in sensual pleasures, the more their sensual craving increases and the more they burn with sensual fever, and yet they feel a modicum of enjoyment & satisfaction dependent on the five strings of sensuality.