If the driver needs to be able to step in at any moment, it's not a fully autonomous car in any meaningful sense, it's just a tech demo.
The only point of a fully autonomous car is so you don't have to drive it. This means (i) being able to concentrate on stuff other than the road, like a book, a movie, or being asleep and (ii) if you're not going to be driving it anyway, why bother acquiring the skill to do so, and the certification to prove you can? Hence, just insurance.
I really can't see the point in buying a car whose defining feature is that it can drive itself, and having to be on stand-by status to take over at any given instant. If that's what we're offered, I would say that whatever Google is capable of cooking up, we're not actually being offered a fully autonomous vehicle.