Environmental concerns aside for a moment, a half-hour or more in a self-driving car is actually more productive/convenient than many city-dweller's commutes - most people could essentially begin their workday in the bubble of a car with a 4G connection and VPN.
Private space is important. So is freedom from interruption. And of course, the fact that trains don't always run on time, and never go from exactly where you are to exactly where you want to be.
