Some of this sounds like it belongs in paranoia!
Based upon what I know of drugs, which isn't terribly much comparitively, I think that things would not be able to carry on as is if everyone was in a constantly dugged state. That said, I also think that many drugs should be legalized. In a country that worships it's ability to carry guns, I doubt that the dangers associated with drug use is the main fear here as the ability to kill/harm oneself with a gun is largely higher than with drugs. I realize that the States have it in their constitution to carry guns, but not drugs, but they also place high value on freedom.
As Trudeau said, "The state has no business in the bedrooms of the nation." If people want to smoke the odd joint, or pop a mind bending pill, it's not the government's business.