I always thought that the people who can't let someone work in doesn't have enough focus. Why would it matter to you what someone else does while you are waiting? It is not your bench. I would agree that if you see a guy with 4-5 plates per side on bench, you let him go about his business and move somewhere else, but most machines and free standing benches by the dumbbells are so easy to change around, who cares if someone works in.