It's foolish to believe that real humans, driving real cars, will treat these technologies as mere "driver-assists." Autopilot is used -- shockingly enough -- as an autopilot. And even if they /were/ used perfectly, these systems are exerting physical control over the car -- something that the National Highway Traffic Safety Administration has a distinct interest in managing. The NHTSA would be grossly negligent if they did not attempt to regulate these devices.