When I'm out and about in L.A. i see a lot of these guys.
I talk to them sometimes. They're not always as crazy as they seem. It's just that the hardships of life has forced their psyche to be in an imaginary situation (talking to themselves)...so that they can accept their fate.
Sometimes they do it to protect themselves. The homeless here, are constantly terrorized by the youth of our generation. It's so sad..
Edit: (disclosure) I've slapped the piss out of somebody's teenage kid over this
. Because i felt the parents weren't doing a good enough job whoever they were so i slapped him. He kept throwing this homeless guys stuff all over the place. So i threw his face all over the place.