Because people all over the world have shown, when they don't feel like they have to pay attention to the road, they won't. Distracted drivers crash into other cars all the time because they're fucking with their phones, or the radio, or whatever their kid just spilled in the back seat. These are people actively engaged in driving the car who "momentarily" lose their focus and crash because they can't orient themselves to the situation in time to avert a crash.

I'd expect that the illusion that the car is paying attention for you would make the situation worse.

Because they haven't been driving the car.

Eternity when driving and paying attention. Blink of an eye when letting the car drive itself as advertised.