Considering how much money has been put into the Washington DC subway system, and it still can't support itself, much less turn a profit, all I can say is that the government just decides to support some things beyond all reason and screw others beyond all reason. If it were not for the subsidies of the airlines and highways, passenger trains would still be a major transportation option. Just think what it could be like if there were "autotrains" going practically everywhere, charging airline-like prices with rent-a-car type prices thrown in on top for the ability to take your own car, packed to the roof with all of that vacation stuff you can't take on a plane.