[sarchertech]

Road damage isn’t like hit points. If a road has regular large vehicle traffic, it doesn’t really matter how many smaller passenger vehicles are driving on it—even if they are pickup trucks. Passenger vehicles aren’t going to change how frequently the road needs to be repaved.

At the extreme end, imagine a railroad bridge. We don’t care about how fat the mice that regularly cross it are.

[AnthonyMouse]

It's not only that. Roads have to be resurfaced periodically because of weather damage regardless of how many vehicles drive on them. For any road that sees predominantly/only car traffic, this will be the dominant effect and the cars are irrelevant.