Cars ultimately need tons of cash to fulfill the high-maintenance roadways needed to maintain their paths. Car companies convinced federal and local government to provide that cash, making little of the investment themselves. But it's not even fully paying for itself - meaning lots of walkers end up footing that bill for systems they don't use.
Even if we end up with a corporate-run high-speed rail network (which certainly does have some of the same issue), it's most logical to pair that with pedestrian, walkable areas in most parts of cities. THAT part is impossible to monetize except by local businesses that just want you to step inside.