If you live in a city like Chicago it is pretty easy to be car free. Being that it is for the most part bike friendly. As well as the CTA (Chicago Transportation Authority) allowing bikes on the "L" trains (except during rush hour) and even on the bus. They have a two capacity bike carrier on the front of all buses.
I never made the choice to be "car free" for higher social reasons. I did it mainly since:
- parking is a pain and expensive usually
- gas is expensive
- I never much leave the city that often
- car insurance is expensive
Another newer bonus is that even the Metra (the train system for the suburbs) allows bikes on them. So you can even visit your suburban friends and ride from the station. None of the trains or buses charge extra for this.
CTA BIKE BROCHURE (PDF)
METRA BIKES ON TRAINS