Interesting topic.
Not long ago there was a talk show that dedicated an hour to a guy that lived on the streets, no vices (drugs or the like), and they gave him $100,000. Within a matter of a few months, he was right back on the streets. He blew it all.
I think that many who live on the streets, figure that is their lot in life. They are comfortable in their dicomfort. If that makes sense.
I had a family member who never wanted anything beyond the very basics. A roof over the head, something to eat once a day. That's it! Heating, A/C, a car, even hot water.... was a non-issue. This person was fairly happy too. Lots of people called them a bum, but if they had a dime, they would gladly give it to someone they thought needed it more.
As long as they don't try to harm anyone, I figure they have a right to live how they see fit. I think they have sharp survival instincts. Smarter than we give them credit for. Efficient living. They don't even get Govt. checks, because they don't have addresses. Grateful for whatever good fortune comes their way daily. If none does today, well, tomorrow is another day!