Also you could add racism. Most of these drugs caused social scares when they became popular with minority communities and so people pushed to make them illegal as a roundabout way to target people they were afraid of.
And until the people employed by the systems that police, prosecute, and incarcerate other people have a sufficient safety net, they will be motivated to prop up those systems.
Because there's a hugely profitable industry in the policing, prosecution and incarceration of people