The following is satire.

Tax revenue would get redistributed on a per car basis.

The real difference is the level of driver engagement and support, of which roads get maintenance.

Road districts want to retain good vehicles & drivers for the same reasons those people want to leave.

Rich drivers are dragged down by poor drivers, but poor drivers are dragged up by good drivers.

There is clearly a winner and loser to the arrangement, but it isn't because the road gets less tax revenue per car.