I saw a special on one of the Boston TV stations a few years ago. It talked about how the homeless can stay that way very easily in the city because there are so many programs that make sure they get shelter, breakfast, lunch and dinner. The only downside was that they had to leave the shelter in the morning, and couldn't come back until just before dinner. If they went to work in the meantime, fine, but if they didn't that was OK, too. There were absolutely NO incentives for them to change their homeless state.
I used to know a homeless guy who lived on what he could scrounge out of garbage cans. He was mentally ill. He was one of those who didn't want to live in a homeless shelter and could not do what it took to have his own place.
I've never lived in a homeless shelter but I know people who have, and they are horrible places, lots of theft and other crime. I think I'd probably rather sleep outside. Thank the Good Lord I don't have to make that choice.
Eventually a group home of nuns took him in and made him caretaker, and gave him a place to stay.