Making something illegal does not help when you are not attacking the root cause.

You need to fix peoples psyche before removing their hard drugs, and if you don't have programs helping them, and instead block them from society, you have a much bigger problem at your hands.

Prohibition of drugs is bad because it opens a unregulated black market, where the products don't have standards, and puts money in the pockets of criminal organizations. leading to vulnerable people being taken advantage of, either through recruitment and promise of quick money, or giving highly addictive substances and activities directly to someone that does not have the ability to take care of themselves.