They are. Except for building highways. Gas subsidies. Gas stockpiling for security purposes. Road Maintenance. Signage. And then there's the opportunity cost of the space lost to parking.
Those above choices? Well they're collective and everyone has to pay for them, because without raising taxes they are much too expensive to fund privately. So even if you ride a bicycle to the train to work everyday, you still get to pay for the construction and maintenance of the highway that driving commuters drive their cars on that you can't ride your bicycle, or any smaller motorcycle, on.