I don't think there are fewer delays in a car. I think people are so used to automotive delays that they just calculate them into the travel time. For example, people have 15 mile car commutes that take an hour every day because of congestion, and just consider that to be their "normal" commute time. But if a train or bus is 15 minutes late one time, people get bent out of shape about it.
Its also funny that if their bus is late because it had a flat tire, they usually blame the bus company. But if their own car has a flat tire, they never blame themselves.