Take a step back and look at the big picture. "No man is an island" which in this case is, one's actions affect other people.
I'm all for recreational use of drugs, alcohol being mine, however, driving drunk doesn't only affect myself, it affects everyone around me.
Moderate use (of many drugs) probably doesn't affect that many people to an extent that it's a problem. On the other hand, look at the effects of Krocodile (don't look at images if you have a weak stomach), you can't tell me that that drug has no affects on Society.
Therefore, some drugs shouldn't be available without heavy restrictions.
We only have to look at the disaster of the Prohibition, and federal agents poisoning alcohol with methanol. People died. A lot of them. And those poisoning murders were done by the precursors of the DEA.
In ideal world, yes. But in reality this is not possible, because people will always find a way to get substances they like to use or abuse.
(No idea if this relates to the burglary analogy, but I thought it would be a helpful point.)