As a (former) airline pilot, I have spent a very long time working with, thinking about, and having my life depend on automation systems. Keith hits the nail on the head describing why GM super cruise, Tesla's "Autopilot" and similar systems are terrible, unsafe, and are likely to kill people: The systems are too good.
Because the system is so good and can work for hours at a time without a glitch, you are simply unable, as a driver, to maintain the requisite level of attention to the situation on the road. It's incredibly hard to monitor an automated system that's always doing the right thing. It trains you to stop paying attention. So you do. I don't care whether your hands are on the wheel or your eyes are staring down the road--the system is unable to monitor where your brain is focusing. So you're going to wander off, and then something is going to happen that the system can't handle and you, as a driver, with no context have to take control and make a decision in milliseconds. This is not a reasonable thing to ask of a human.
In aircraft, this is basically never a problem. Autopilots fail all the time, but it's easy for even an asleep pilot to wake up to the sound of an autopilot disconnect warning, maintain or recover aircraft control, asses the situation, and take appropriate action. It's more difficult in something like an autoland situation near the ground, but such situations are short periods of flight where pilots are absolutely ready to take control in an instant--and all they have to do is initiate a rejected approach and go around.
Aircraft pilots are not immune to accidents resulting automation failures. There's a lot of real bad commentary about Air France 407--that's not the one to focus on. Asiana Flight 214 that crashed short of the runway at SFO is the one to look at. In that incident, the pilot flying crashed an airliner short of the runway because he got slow on approach and didn't notice.
Why? Because he was very used to flying an approach with an auto-throttle system. A really good auto-throttle system. Normally pilots are focused on two things when flying an approach: (1) airspeed, (2) approach path. In visual conditions such as this, you maintain the correct approach path by simply looking at the runway and manipulating the stick or yoke so that the sight picture of the plane flying at the runway looks correct. You maintain airspeed by moving the thrust levers in response to airspeed fluctuations on the airspeed indicator. You're constantly looking outside at the runway, then glancing back inside to look at the airspeed.
When an auto-throttle system is engaged but the pilot is otherwise hand-flying, you set a speed bug to the desired airspeed and the auto-throttle moves the thrust levers to maintain the desired airspeed. Initially, the first few times you fly with an auto-throttle, you'll do a good job of watching your airspeed just like you always do. Look at the runway, glance at the airspeed indicator. Repeat every couple of seconds. But as you do this, you unconsciously learn that the airspeed is always correct. So, naturally, you spend more time focusing on the thing that needs correction when you look at it--your flight path, because you're hand-flying. Eventually, the autothrottle system trains you to stop paying attention to the airspeed because every time you glance over at it, it's bang-on, so unconsciously you just stop looking at it without even realizing it!
On this Asiana flight, the pilot flying was new to the aircraft, thought the autothrottle was engaged, but it wasn't. So he flew the approach and for a stupid period of time, paid no attention to the airspeed indicator. Didn't pay attention at all until he was too slow to correct while too close to the ground and crashed a perfectly good airplane with some terrible piloting. Terrible piloting that a really good automation system trained him to do, unconsciously.
In a car, you're pretty much always seconds away from a potential disaster. If the self driving system successfully navigates down the Interstate system for hours at a time, it's going to train you to stop looking at the road. No matter how much you intellectually and consciously know you need to pay attention--you're not going to be able to. And that's going to be fine almost all the time, because the system is good almost all the time. But almost isn't good enough, and it's eventually going to give up working at the worst possible time and you're not going to be able to save it in time. It's not going to fail when there's no traffic and the road is straight and you can safely take over with no context. Nope, it's going to fail when things get tricky--when the road markings are contradictory because of construction, when another car does something completely unpredictable, when visibility or traction are poor or other situations. And then you've got a few milliseconds to save your own life. Good luck.