Treating a symptom instead of the cause is stupid, especially if the symptom (drug use) will likely return as soon as they return to the streets after rehab/prison.
And that help should include mental healthcare and a support structure.
That being said, addiction is not easily cured with or without free housing, if the substance of addiction is easily available nearby (alcohol, drugs, casinos) without additional support systems.
Have you ever used drugs? Drugs are fun. Until they aren't anymore, then they cause problems, like becoming homeless. That drugs are mostly just a symptom of homelessness is such a weird assertion that keeps getting tossed around.
This person likes doing drugs and has no intention to quit: https://archive.ph/wnTq6 But she'll happily take all the free stuff you want to give her. I'm not saying this is every homeless person. But let's not pretend like it's none of them either, and create policies accordingly.
I'm all for housing first. But there needs to be a filter imo to pick only the people with an actual chance of success (which so far turns out to be a pretty low % in LA's program, but still great for those people and I'm all for it).
Also there has to be some consideration for the working/lower class people who live in these neighborhoods. If the people making the policies and those making loftiest arguments online actually had to live amidst all the chaos, I think we'd see a very different approach.
Drugs put you in a place where you prioritize getting high over paying rent. And so it goes.