Earlier quoted context omitted.
Cheap trains everywhere doesn’t have to mean high speed rail everywhere. You can have slower cheaper rail infrastructure that serves less traveled routes.
It also doesn't have to be profitable. Transportation is a service that's critical to economic function. There's no reason not to shift the cost of taxpayer funded vehicle infrastructure to transit infrastructure.
So there is never any economic need to transfer the cost of using the transportation network from those using it, to taxpayers at large. In fact, socializing costs of transportation is what can cause economically non-viable transportation services to grow in usage, and in doing so, burden the economy with loss-making transportation.