That's true, and it blows my mind that that's the first or even high on the list of "ways we can help with this".

I do think there's a Venn diagram around severely mentally ill and untreated mentally ill that might require more intensive care. There's also the complexity that drug use and abuse is a method to cope with the emotional pain of homelessness (as one of my instructors said, "if my existence was reduced to fishing rained-on food out of trash, brushing cigarette ash off of it, sleeping and shitting in alleyways, often without something to effectively wipe with, you better believe I'd be on a fast path to taking some drugs to numb that"), or for "self-medication" of said untreated mental illness.