Perhaps a more exact question would be “Why do some seek to force others (namely non-transit riders and people who don’t want to live near trains) to subsidize the lifestyle they like?

Why do some go to government to finance these types of developments with taxpayer dollars but other non-mass transit oriented developments don’t receive such benefits?

Here’s an interesting tidbit from a Cato Institute study called Does Rail Transit Save Energy or Reduce Greenhouse Gas Emissions? “Far from protecting the environment, most rail transit lines use more energy per passenger mile, and many generate more greenhouse gases, than the average passenger automobile. Rail transit provides no guarantee that a city will save energy or meet greenhouse gas targets.”

http://www.cato.org/pubs/pas/pa-615.pdf