Yes. At many stages of the descent from "I'm just crashing on your couch until I save up enough for another deposit" to "I'm sleeping in my car until I can find a job" to "I'm living in a shanty and rummaging through the trash to turn in aluminum cans for change". Both whilst living in the Bay Area, but also in Oregon and Washington.
You're complaining (rightly) about the end stage. I'm saying that nobody starts at the end stage.
Hell, I'm actively watching my brother-in-law and his baby mama descend through the mental illness and addiction process, and even though they've been evicted and are now dragging their daughter through the couch-surfing phase, they still aren't at the living-in-tents-shitting-on-the-street phase of that descent.
And a major factor, for them was that neither of them could get the kind of jobs that would allow them to both have a stable living situation and do anything but work (because of criminal history resulting from addiction). Its a cascading series of problems that when he lost his license (due to his addiction), he could only work where he could walk, or where he could realistically ride a bus. And in most of the country, if you can't find work within those two ranges, you're shit out of luck.
And to be clear, I'm not proposing we just throw up our hands and say "I guess they're just addicted and this is our life now". I'm saying that "just lock up the homeless people" is as much a solution as "well, we've got seatbelts" is for a hydroplaning car. We have within easy reach the ability to 1) stop more people from becoming homeless, and 2) help people who are homeless get their lives back in order.