And that's the thing --- if it's just augmenting a human driver, it means that now, instead of driving, you're supervising. And that's a much more difficult thing to devote continuous, full, unwavering attention to (still required) than it is to devote that attention to something you're actually doing yourself.
I have yet to feel safer in a car that argues with me than I do in a car that just lets me drive. And until it can take over *fully* from me (which it may never), I would rather it not express opinions at all.
Except, specifically and only, adaptive cruise control, which is strictly better than regular cruise control, and which still leaves me steering.