This is why a Comma.ai style system putting a camera facing the driver to make sure they are paying attention and awake is essential. Even ignoring self-driving a big number of accidents happen when people fall asleep at the wheel.

I’m not sure whats stopping them. It can be done locally to avoid privacy concerns.

It also has better UX than the weird wheel touch sensors on some vehicles where you have to be touching the wheel at all times when activated (I haven’t decided if that make sense as a requirement, leaning towards no).