The problem isn't with substances per se, but with the fact that people react differently to them.
Nothing is addictive to everybody, so one tends to not abuse things that are not addictive to oneself.
I like many kinds of alcoholic beverages but never drink immoderately.
I've taken opiates in situations of extreme pain and not even looked at them once I felt better.
I was totally addicted to cigarettes, however, and getting off them thirty years ago was a brutal experience.
I suspect that were I to smoke even one, I'd be on a pack and half of Camels each day in no time.
Yet I knew plenty of people who could enjoy a cigarette with a drink or a cup of coffee and not have another all day.
Whenever the government decides to proscribe something, it unnecessarily restricts the freedom of a lot of people,
and the ones who should avoid the proscribed substance the most will be the ones who still find a way to partake of them.