Where has the hitch hiker been and why

The driver leaves, and as he approaches the truck, the hitchhiker asks for a lift. The driver asks him if he saw the No Riders sticker, and he replies, "Sure - I seen it. But sometimes a guy'll be a good guy even if some rich bastard makes him carry a sticker." The driver lets him in and examines him closely as they drive off. The hitchhiker just got out of prison for homocide.