> We’re a quarter of the way through the 21st century, gas taxes have been optional for driving for quite a while now.
States mostly take the equivalent of those taxes out of vehicle registration fees for electric vehicles.
And bicycle usage is nearly a nil cost on the existing public roads, so the costs here would be appropriate to come out of the general sales/property taxes that fun the city/county. If anything you might argue to try to subsidize bicycle ridership more in urban areas, whether with bicycle paths or otherwise, to reduce the number of cars on the roads and reduce congestion for those still on the roads.
The cost of adding one more car to existing public roads is also essentially zero, as is the cost of adding one more rider to an existing bus route. Until you hit some tipping point and need to add more capacity, then it costs a lot. Bicycles can do that too, if a significant number of them shows up.
In any case, the point is that public transit riders pay fares. Not taxes, not registration fees, but fares. The equivalent for roads would be tolls. And it’s pretty uncommon to see any advocacy for charging tolls for all roads.