The railroads pay property taxes on their rail lines and facilities, to include the train stations. The airlines don't have to worry about that expense in relation to airports.
The government has a nasty tendency to penalize success.
Because if it is a significant amount, say, 15 to 30 percent of their gross revenues, then all the Feds have to do to have a first-class rail system up and running by 2010 is to simply rescind all their taxes.