Freeways also subsidize commuting. Would people sit in traffic every day if they had a choice? But if you suggest dynamiting a few stretches of interstate you get the same reaction from the public as you get when you suggest taking away prop 13.
Would people sit on public transportation every day if they had a choice? Cleary not - BART ridership is falling during leisure time (when people have a choice) even as it rises during peak hours.