Because everyone benefits more from roads that are less congested. If everyone rode bikes or the bus 90% of the time, there would be mostly empty roads in the

Because everyone benefits more from roads that are less congested. If everyone rode bikes or the bus 90% of the time, there would be mostly empty roads in the 10% of time that they do use a car. If you had to pay a significant price per km in congested areas, you'd probably drive less, but it would be a nicer experience when you do drive.