Bike commuting during winter is fine as long as you have the right clothes. I have commuted in a -55F wind chill in perfect comfort. I will concede that it takes a few weeks to calibrate clothing if you're not used to it, but it's not some huge barrier if it's something you're interested in
Snow cover can make it impossible. Frozen rain means you need somewhere to store your wet clothes, and they will not be nice to put on when going back. Somebody who isn't a huge biking freak will prefer the car.
