The reality of drug laws in America is cops and prosecutors mainly use them to target criminals actually causing the community problems. It very rarely happens that an otherwise innocent casual user does time for possession. The system is arguably less broken than internet libertarians think.

It's often surprisingly difficult to prosecute somebody for repeat breaking and entering or gun violence, but the cops generally know who is causing the problems, so they get them on drug possession. This is where the crack cocaine sentencing disparity comes from. Crack affected communities demanded the law get the gang bangers off the streets, and crack possession was the obvious way to pop them.