The difference between drugs and most other crimes like robberies or extortion is that drugs have a huge demand side as well as a supply side. Your idea seems t

The difference between drugs and most other crimes like robberies or extortion is that drugs have a huge demand side as well as a supply side. Your idea seems to be that the illegal drug trade is a sort of daycare for criminals, and there's a certain fixed amount of criminals that will do illegal things, and therefore switch to the next-best illegal thing when the previous one gets legalized. I think that's unrealistic when you consider the money that incentivizes people to go into the illegal drug trade.