The reasons behind why governmental organizations pass laws controlling the sale, distibution (or prohibition thereof) and/or use (limits such as blood alcohol limits) of various intoxicating substances are not limited to only three categories.
Careful - YOUR ANSWER may parallel mine from earlier - and we can't have that now can we ...
It doesn't.
Sure it does.
You're just unwilling to go there. Or anywhere near it.
When I'm right - I'm right.
And you're wrong, incorrect, off-track - playing some sort of game that defies logic and common sense.
Failure to accept certain fundamental truths or basic concepts that underlie the motives or desire of, say, our law-making bodies as applies to their reasons for passing certain drug-laws is, well, living in a fantasy world ...
But hey, that's your choice, not mine.