I'm not speaking in absolutes here obviously. But it's pretty well established that a very small fraction of people who take drugs (prescription or otherwise) become what we term addicts. There are lots of affluent addicts and alcoholics (I know plenty personally) but just because they have access to medical and mental health care doesn't mean every one of them will go there.

You don't see a lot of upper middle class people end up on the streets with heavy addictions because they can usually get into rehab, get help processing whatever it is keeping them down, and move on with their lives. Lots of poorer people can do so as well (the poverty and "success" porn content out there is easy to find) but for every one of those success stories there are thousands who never make it. I don't think it's hard to parse that poorer people have less culturally acceptable means of getting help (if they don't outright end up in prison for simple possession to begin with, which I'm guessing those peers you're referring to seldom have to worry about).