Personally, I think the root of society's issues with drugs is rooted in moral judgment. It's our nature to be compelled to engage in certain activities (reproduction, sleep, obtain food) yet collectively rules and standards have been created to select which ones are okay, casually speaking.

It's not so much as "why can't Americans go without" as much as it is a "why can't Americans admit Prohibition doesn't work" type of question to me. The latter is a lot easier to fix than the former, I think.