Should they? Portugal has had a lot more success managing drug addiction by legalizing things than through prohibition.
And none of those were Federation planets with access to advanced treatments for addiction.
A new and unfamiliar drug for which no addiction treatments had yet been developed, on a ship stuck far away from the medical industries of Earth or Vulcan.
And we never once saw any indication that the drugs she used were illegal.
Agreed that Turkana and Ornara didn't have the resources to combat addiction, but Turkana used to be a Federation colony. Clearly, something happened that made them a failed colony and the drugs, gangs, and all the other problems became commonplace. You'd think they would have kept at least the medical side of what they got from the Federation around after all that happened and used the knowledge against addictions. (Since we don't know how their government fell apart, we can only speculate.)
And my point about Raffi being an
addict on Earth was that drug addictions
still happened. Even in the paradise that is Earth. Whether the drugs she took were legal or not is immaterial. So yes, drug addictions are apparently still a thing in the 25th century, so that can certainly be an issue from the 2200s until that time.
And about having drugs all being legalized... look at Portland. By decriminalizing drugs, you get a sharp spike in crime. Theft, assaults, and murders related to addicts getting the money to get their next fix is a big problem. Granted, that happens anyway, but the degree it occurs when you decriminalize drugs is hard to ignore.
And frankly, drug dealers are predators... they are preying on people with items that gets you high and addicted. They are like tobacco companies... cigarettes have been known to cause all sorts of medical problems, not the least of which is extremely high addiction, for the users
and people around them for DECADES. They are another kind of predator because their product has absolutely ZERO positives and they get people addicted so they can just keep buying more and more.
Saying you are fine with drugs being decriminalized is akin to saying you are fine with predators going after people.