The average number of people in a car is probably somewhere between 1 and 2, but if a group of people who know each other have to go from A to B, it is reasonable that they may try to get in a single car. If nothing else, because parking in major cities tends to be a nightmare, and finding a spot for one car is easier than finding N (reasonably close) spots for N cars.
> If nothing else, because parking in major cities tends to be a nightmare, and finding a spot for one car is easier than finding N (reasonably close) spots for N cars.
A vehicle which isn't moving is not performing its job as transport; and is instead wasting space. Your scenario is better served by public transit, which doesn't require any parking (outside of official maintenance depots, etc.). It also scales to groups of several hundred, whilst a car can only take around 5 individuals (perhaps a few more in a minivan, but that just makes the inefficiency of moving it around and wasting space on parking even worse for the entire rest of its lifetime!)