Alcohol use exerts enormous tax on society which chose to tolerate it for historical adoption reasons. Adding hard drugs is going to exacerbate the situation, and a number of those are worse than alcohol by any metric imaginable.
Alcohol has been with us for millennia, with cultural references going back to Homer. It is deeply embedded in our social fabric. Perhaps at some point it would be banished like tobacco is now. But it makes little sense introducing the prohibition when the bulk of society isn't on board with it.
