What is the materialist explanation of the War on Drugs?

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?