People on the street are often using street drugs in place of prescription medication, sometimes by preference because, for example, they have a psych diagnosis and street drugs have preferable side effects to the medication they are supposed to be on.
I knew a bipolar man somewhat well who was homeless. He smoked marijuana in preference to the prescription drugs he refused to take. He was unemployable due to his undamaged mental health issue, not because he toked. Toking was just how he got by. He wouldn't have been more functional without pot. He likely would have been less functional.
We still don't have a slam dunk cure for most mental health issues. As long as this remains true, it is problematic to act like addiction is not merely a side effect of the problem and, instead, to pretend it somehow causes the problems an individual has.
Saying addiction is the problem is a little like blaming chemotherapy for ruining someone's life and not acknowledging the underlying cancer as a problem.