How many homeless people have you talked to? In my (anecdotal) experience just chatting with people, there are plenty of “lost my job and now I’m homeless” folks in SF. These tend to be a bit less visible than the mentally ill though.<p>More generally, many homeless people become mentally unstable or take up mind-altering substances after a while living on the street. It’s a really stressful, socially alientating situation, and in general the folks who end up homeless are those with less family&#x2F;friend support. When you’re stuck feeling like a social outcast with no particular purpose, under the daily stress of figuring out how to eat, find a bathroom, sleep, shower, etc., it’s hard for even the toughest person to stay mentally sharp and optimistic.