I don't get it. Doesn't autopilot mean that the car is steering itself? "Perfect" or not, if the car is steering itself, what is the point of having your hands

I don't get it. Doesn't autopilot mean that the car is steering itself? "Perfect" or not, if the car is steering itself, what is the point of having your hands on the wheel? I get the point about being alert, and needing to take over if you see an issue, but I would fear that I'd be overcompensating autopilot by having my hands on the wheel while cruising along. Can somebody explain?