It's true, there's probably not a whole lot of direct profit to be made from it. Americans just aren't that psyched about the train (because: see my earlier post). In order for it to be popular, it would have to be significantly cheaper than an airplane, which Amtrak often isn't.
It could potentially offer a good deal of indirect profit, in the same way that a bridge over a difficult chasm would improve transportation and therefore business, but the only organization that would invest in that is the government, and right now it's pretty far down on the list of priorities.
To make one last point, I'm from Maryland, and for the year and change that I lived in Indianapolis, it was quite a shock to have so little public transportation. Indy has just a bus system, which is about on par the one on campus at the University of Maryland. In DC, I could just hop on the Red Line and head down to the Inauguration, or the Jon Stewart rally, or my Jeopardy audition, but in Indianapolis I stayed away from the Super Bowl (!) because I knew it would be a tremendous pain in the ass to park.