The price of a bus is roughly 10x the price of a car.

The average number of passengers in a car is about 1.5.

So the average number of passengers in the bus has to be over 15 to be more cost-effective than a car. 15 passengers is far from full. And it is on average, not most of the time.

For the space the passengers take up on the road, it is even more extreme. Take a look at how far apart cars drive on the road. About one or two cars take up the same space as a bus that can carry dozens of passengers.