Humans vs Trash Cans

Listen here, you're one of those people who walk into a room and lower the IQ. You clearly didn't understand this simple concept, so here goes. This joke compares human to trash cans. The funny part is that humans are considered less useful than trash cans. The joke implies that humans are useless and that makes people laugh because that's a funny thing to think, even if it is not true. Got it?