Capitalism has a deep-seated taboo against taking recreational drugs. So strong is the taboo they will ruin your life and exile you from mainstream society for doing something recreational.
This is changing a bit as the scientists tell them there is basically no reason for this. But the scientists meet with resistance from entrenched cops, judges, lawyers, who are very 
about it.
What's the materialist explanation for this moralistic taboo?
(CW: n-word slurs, racism)
https://www.thenation.com/article/archive/exclusive-lee-atwaters-infamous-1981-interview-southern-strategy/
I believe that's most of it at a material level. Years before legalization was even a thing in many states, when a bunch of affluent white kids get pulled over for speeding or drunk driving, the weed stink got a verbal warning, if that. Compare that to the sentences (and career-prospect ruining aftermath) of "urban"
kids getting caught smoking a joint.
Also, notice how there's just about zero enforcement of anti-drug laws and policies if it's white (or "honorary white") Silicon Valley techbros trying new and exciting custom drugs (particularly on their economically coerced company) at their little SV parties?
(CW: SV)
https://www.vanityfair.com/news/2018/01/brotopia-silicon-valley-secretive-orgiastic-inner-sanctum
The so-called "war on drugs" is a war on the poor and on minorities. The material goal is to oppress the poor and minorities and keep the flow of prison labor coming.
Glad to see the Atwater interview mentioned, that's largely how I view the purpose of the war on drugs. They can't make it illegal to be black or poor, the war on drugs is the loophole for that.
Not to mention, I'm sure there's some influence from the legal drug industry (alcohol/liquor and pharma) at play.