The criminal record is another problem, along with the actual experience of being in jail. Making a mistake should screw up a person's future, which therefore increases desperation and the likelihood of doing drugs (or selling them), etc etc. Great system, real nice. But of course it is really nice if the actual objective is to have many people in prison, which I do believe has been the case. Many countries have drug laws; only one has the prison population the U.S. does. Something doesn't fit.
Aside from the legal aspect of it, the banning of any drug automatically leads to a black market which creates a lot of crime, border problems, soaring prices for people who are inevitably going to seek that drug anyhow, huge financial gain for any person (in government) who makes deals with the cartels, serious chaos in the countries supplying the black market; and the list goes on. Whether or not hard drugs 'should be' illegal on some kind of moral grounds, on a pragmatic ground I suspect more harm is done by banning them than would be done by allowing people to legally destroy themselves with them. I honestly don't think it would end up being as bad as people think; especially so because part of the problem with drug culture now is the need to keep the illegal activity hidden, which therefore often leads to problems becoming untenable before a person seeks help and admits the problem. This is all speculation, of course, but if one tallied the net deaths causes by current drug laws (in the U.S. and abroad) I would put down serious money that even a drug-use 'epidemic' under blanket legalization would still not equal what's happening now.