As I said, those substances are natural, for many people they would be beneficial as well for some specialized uses, like improving one's medical condition. But leaving humans in pure nature "as intended" destroys civilization - regulating behavior is necessary (even if I personally don't like it and tend to think "I know better" when I don't).

I would propose an experiment - let's look into history and see which civilizations propagated and which went extinct or ended up zombified in a non-progressive isolated state. I'd bet there will be quite a few where "substance abuse" went through the roof, and those that restricted it either completely or moved it to a dedicated "crazy week" (Bacchanalia?) prospered and progressed. Seems like hardships are necessary for progress/motivation(?), short-circuiting pleasure centers with drugs doesn't move society towards higher complexity and beauty.