We made alcohol illegal once already (and it required a conditional amendment to do it) it was an unmitigated disaster. It gave rise to a criminal class the likes of which we had never seen before. It created more damage to people that acquired it illegally because it's pretty hard to go after a criminal that was selling bad alcohol. Not only that but the people that drank to excess still drank to excess. A basic knowledge of history would demonstrate to a school child that making alcohol illegal again would only create more problems. No problems you mention would be alleviated by making it illegal.
I do not see the constitutional authority for the government to ban any substance. That being said, people need to be responsible for their actions and with our welfare system we would end up paying people to take drugs. I would think that is a bad idea.
