Both cases of sleep and hunger are demonstrably untrue, for we can turn off those systems (with modafinil for sleep, and ECA stack for hunger), and there are few ill effects.

The fact that we can alter our psychology with drugs does not change what that psychology is. We can also eliminate or cause many emotions and perceptions, and will probably learn to do so with for a larger variety of cases and with less side effects as time goes on. These drugs are properly considered as an extension of willpower, not a counterexample to it.

These systems are horribly misregulated, and cause more problems than they save from.

It only seems that way because of availability bias; we only know these systems when they go awry.