Another major hurdle is the petrol industry & incentives for the few to get rich my building & maintaining roads. Public transport on the other hand (hopefully) doesn't generate profit as it is a service for the people. So those in local/regional/state power have more to benefit (personally , financially) from building roads. It's like taxes, people that influence/write/adopt tax policies are the ones that benefit from tax cuts whereas the majority loses more through all the services they have to pay double for.

It takes civil organizing to produce politicians and high enough demand for such change. Often through things like higher commercial rents or local service fees (like stores in the center pay more for water or waste disposal as they would in a mall outside the city - and the difference pay the customers though cars, time, and well-being).