The few dozen actuators we can fit into a robot have a hard time managing that. We just don't have anything that adequately simulate muscles. Our motors and pistons can to incredible things, but they just don't behave like muscle...

Next, humans have this weird brain thing, connected to thousands of sensors. It has many flaws, but a thing it's very good at is interpreting and reacting to the environment. We have some pretty cool sensors and processors, but nothing can even approximate what our brains do casually...