Some people here are car-free for economic reasons mostly. I'm not car-free as of yet, but I plan on selling my car after I complete my bachelor's degree and move out on my own, also for economic reasons. Plus, riding a bike is just plain fun. It's way more fun than driving is for me. That's my main reason for wanting to be car-free, not for the environment, or fitness, or whatever.
Of course, if you still don't believe the evidence of global warming, then I hope you'll enjoy the hotter summers we'll be getting in the coming years. Hell, right now, down here in So Cal, it's gotten to almost 90 degrees at the beginning of March! I don't remember it getting this hot at this specific time last year!