Why do poors like to hang around dumpsters?

My office building has an Episcopal church next door. Wednesday is their freebie grab day where ppl can come get food, clothes, rent checks, etc.

There's always hordes of people in the parking lot and hanging around all day. They typically gather up at our dumpsters or the church's. There's perfectly good spots on the church grounds or other areas nearby but they always go to the dumpsters.

Any logical reasoning?