People use cars instead of buses or trains whenever they can. Often they will sit alone inside their large heavy box on wheels, not moving, polluting the environment and wasting energy, while looking at hundreds of others doing the same.
Yet everybody complains about doing it.
This is strong evidence that there is an ongoing  love affair with the automobile.

Many attempts have been made to entice car users onto public transport.
Expensive and elaborate mass transit schemes have been constructed.
This gave people already using public transport the benefit of switching to a better public transport system.
In general, people will not leave their cars for another mode of transport. (See Related Sites for some case histories).
This is the reason why some light rail schemes have failed: they merely bankrupted the bus company while the roads filled up with more cars.