Morality aside, I think widespread drug legalization will greatly increase usage rates. It could lead to a more dystopic future where a very large portion of people are using various drugs.
Cannabis and mushrooms, to name some, have been considered and succesfully used as versatile medicine for thousands of years, only to be banned about half a decade ago. Only the last few years this is starting to change, as more and more research shows the medicinal benefits, while debunking most of the lies that have been spread.
Psychedelics 'cure' consumerism, make one more sovereign, enable independent thought, and help you break destructive patterns, by making one see through their life-long conditioning. They make us better people, but worse consumers who need less medicine.
It's quite obvious why these substances are banned, as it's not in the interest of the state to have a flock capable of independent thought, that does not consume a lot and doesn't buy words of division and fear. To clarify even more: the only legal substances are those that cloud our thoughts and make us stupid and dependent, like alcohol or prescribed anti-depressants.
(btw I support legalization of cannabis and other psychs)
It was also the case that it's not cannabis that introduced bad habits, it was that the bad habits led to (the need of) cannabis use to ease my mind.
Now, I use it as a tool for creativity, when I'm working with my music.
I would also like to share this video, about how addiction seems to work: https://www.youtube.com/watch?v=ao8L-0nSYzg
I personally never liked it that much so I can't see myself being a frequent customer. Haven't touched it in years despite it being 'around.' I will probably go have a first legal toke though when it's legal here (California) just because.
We will wonder why on Earth we ever spent billions of dollars and locked people up in prison to suppress something so... trivial. On the bright side, when it is made legal and nothing much happens all the histrionic drug warriors will look unbelievably stupid and everyone will laugh at them. That's a good thing.
I think as a society is more progressive/efficient to help and support those with drup problems as apposed to locking them up and creating an industry for the trade of 'illegal' drugs. What a waste of time and resource playing cops and robbers for 'drugs', I hope more and more policing groups are noticing this and feeding back over time.
Alcohol is legal in most countries and is widely consumed, certainly much more so than it would be if it were illegal. It can be very addictive, and it an be very destructive, like many drugs which are currently illegal.
I agree use of drugs would probably increase overall, but that society can adapt without collapse. Many people take illegal drugs now from time to time, and are able to function and live normally, have jobs, and not have their world implode.