How are you going to make it illegal for the person who gets shitfaced four times a week without forbidding it for the hordes of people who have a glass of wine or a beer with dinner, or for that matter a shot of scotch twice a week?
And how, in practice, are you going to prevent the shitfaced person from getting shitfaced anyway?
And how, if it’s all illegal, are you going to make sure that what’s on the label is what’s actually in the container, thereby preventing people from accidentally poisoning themselves and/or winding up a lot drunker than they intended?
Nothing that humans want to do is entirely controllable; but legal things are a lot more controllable than illegal ones. We learned that one during Prohibition.
Yes, here are some things I listed in that post that need to be weighed:
the benefit of that behavior to the individual
the benefit of that behavior to the perception of freedom
the risk of using the government’s power (potential for abuse)
the collective external costs of dealing with that behavior, etc
Most societies have weighed various factors and decided that it’s best to keep alcohol legal and deal with some of the worst aspects through general taxes.
Most societies have done a similar debate over heroin, and decided that it’s best to keep heroin illegal (although increasingly in progressive countries, not strictly criminal), knowing that’s not a perfect solution.
You can’t make blanket statements about drugs. Each one has to be weighed individually.
Some people feel the need to control others “for their own good”. To quote the (possibly apocryphal) line from Ambrose Bierce (or H. L. Mencken), the definition of Puritanism is:
“The haunting feeling that someone, somewhere, might be happy.”
I think this motivation is often blended with the general disgust reaction that people have regarding the actions (or sometimes mere existence) of others - “people should stop doing that, it’s bad” is not really all that different from “people should stop doing that, I find it disgusting”.