If you function well and are happy, why not?
Drugs were made illegal because ”they were thought to be dangerous to the establishment” in the form of African-American and civil liberties activists, both of which were easy to label stereotypical drug users with a bout of fictitious press.
Another political reason was the historically open international trade which did end up with the Opium Wars in China — but that precedent was used as a propaganda tool first and foremost, since the real reason for the war was not opium, but Great Britain’s heavy-handed imperialist approach to trade.
The irony is that these conventions are enforced with a similarly heavy hand and with equally imperialist policy behind it.