Since we think certain people are up to no good anyway, drug laws let us put them away, without actually having to prove the bad things they've probably done. It's essentially an end run around "proof beyond a reasonable doubt."
Laws criminalizing concealed weapons follow a similar logic.
I don't think it's the drugs that are the problem, but the way people use (or rather abuse) them, and the conditions that drive people to abuse drugs.
Lots of social conditions are bound up in problems for which drugs alone are blamed. Too many people are poor, desperate, lonely, outcast, downtrodden, hopeless.
These and other social ills are what encourage drug addiction (and other types of addiction and destructive behavior), and they are the things that society will have to squarely face and overcome before they can effectively treat addiction.
Merely making drugs illegal hasn't and isn't going to work. Locking people up for seeking a way out of their misery hasn't and isn't going to work. Merely making drugs legal isn't going to work either, but at least it isn't making the problem worse or adding all sorts of other problems to it.
One day you're an addict, the next day you're an addict and shot by the police or in jail and your life is ruined and it's likely to get even worse once you're out. That doesn't help anyone.
Trump being the best example in the US, and other oligarchical systems in all other countr.
Money is the root.
Or as George Carlin puts it best:
As for the public health implications, there's probably way more effective ways of mitigating that than making them criminals. It's a range though, those that cause significant harm to others should certainly be taken out of the system. Alcoholics are frigging annoying, and highly disruptive, but many aren't actually violent criminals.