Imagine a six-foot tall plastic punching bag shaped like an orotund man and weighted on the bottom. Punch him if you wish, you’re not going to hurt him. Send him to the floor and watch him pop right back up, oscillating a while before he’s still. He knows up from down. Gravity acts on him in a predictable way. He does not have the advantage or disadvantage of joints. Let’s give him some. Let’s give him toes and ankles and knees and hips, a jointed spine, and an atlanto-occiptal joint on which his head rests. Suddenly articulated plastic man has some issues. Without your full-time external maintenance, articulated plastic man is going to wallow in a puddle of plastic on the floor. Poor fellow.