It's bad to trash a shared living space.
Gary and Greg are roommates and Gary decides to have some beer and pizza tonight.
Gary wants to enjoy himself.
Gary drinks his beer and eats his pizza and makes sure to throw all the empty cans and pizza box away when he's done.
Gary drinks his beer and eats his pizza, but leaves the cans all over the room along with the empty pizza box laying out.
Greg appreciates Gary doing his part to keep the apartment looking nice.
Greg thinks Gary makes their apartment unsanitary and begins looking for someplace else to live.