I dunno why you'd tell your self-driving van to do laps for eight hours when it could just drive somewhere outside the city and park, unless you live in a city where the commute time is more than four hours each way.
What would it matter with a self-driving car if the commute is four hours? No-one will care. Notice how it's often "worth it" even now to drive for half an hour or so to get cheaper fuel. Except, with no rent in the picture, it will be far more worth it. Add to that that Americans aren't willing to give up bigger cars ("easy-ish" to live in) and ... Self-driving will just become a way to use more public resources for specific people.
I just pity the people who still expect to normally get through traffic.
It would matter because sleeping in a moving car in traffic in the middle of a city sucks in comparison to sleeping in a parked car in a quiet street on the outskirts, and also uses more fuel and wears out the car faster. There's no gain to driving around in circles while sleeping compared to having your car go and park somewhere.
If the cost of fuel and car maintenance are lower than land and house, it's inevitable.