They do move around, and are typically arrested and ticketed by police for doing so. If you were to move to a suburban area a resident would complain about the hobo pushing a shopping cart and squatting in the woods so you would find yourself being given a "starlight tour" which is when the police drive you to the middle of nowhere and kick you out of the vehicle at 2:00am.

You have friends there. You can live without a house, but you can't live without friends.

The better areas are taken by those with money. You can move to a better area, but the police will turn up before long to move you on.

Obviously is not a simple life. Dangers are everywhere from drug dealers to policeman. But to keep this short the fact is the same: For a mentally sane man (or woman) in USA is very difficult die of starvation.

At some point the assumption of sanity breaks down, in this lifestyle.