Fentanyl and xylazine are only common because of prohibition; legalize all drugs, and opiate users will flock to heroin instead.
Also, the necrosis isn’t caused by the drugs themselves, it’s cutting agents, needle reuse, and poor sanitation. Legalization solves the first one, almost solves the second, and makes teaching about the third a lot easier.
5ml of vanilla is a lot easier to measure than by weight would be