The problem is that mass transit isn't a viable alternative in many places. It works out great in big cities (if the infrastructure is in place), but if you live out in the country, smaller towns or in an area of suburban sprawl, mass transit isn't practical now and likely never will be no matter how much you invest.

When I was in Boston for work many years ago, it was great to be able to take a train from outside the city into downtown for a couple of bucks (though you would still need to get transportation to the train station...in my case there was a stop right outside my hotel). But living along the Space Coast of Florida, mass transit is not a viable alternative to a car and I'm not sure how it ever could be. Complementary maybe, but definitely not a replacement.