as no-one who isn't addicted to the substance will take the risk of procuring it illegally. And the ones who are addicted obviously require medical care.
More mastubatory logic there. If that were true, there would be no users of a product withing a generation of banning it.
The decrease of organised crime in drug trade is no argument, one could argue that murder should be legal since the amount of convicted murderers goes down if it is legalised.
If murders only harmed the murderer that might be the case. The use of drugs is nominally victimless. And the only decision we need to make about a popular product in a free society is do we want CVS or Walmart selling it or organized crime.
Not to mention how the ban on certain drugs in America isn't designed to lower the usage of drugs to begin with, rather simply profit off it in various ways.
It has had that effect though.
Recreational drug use serves no such purpose and only exists to numb one's mind from the outside world, and likely their troubles, this fact just is covered by pretty words about "relaxation" and such.
Many leisure activities serve no immediate purpose other than relaxation. I see you've ignored the socialization aspect of recreational drugs and their effects on the various arts too.
Also only half the drugs roughly "numb ones mind." Those are downers. Uppers increase brain activity.