As someone notes above, I do bike to work, more and more as the months go on. I went from intermittent a few years ago to daily when weather is comfortable. This year, I'm going to try to do it through the cold as much as possible. Still not sure how to handle the ice and snow, but I got glove liners, a balaclava and a few other cold-weather items just yesterday.
Why ride? I live insanely close to work. It's five minutes by car (as the blog title "My five-minute commute" implies), seven to 10 by bike, depending on my route and mood. I don't buy a parking permit (I work at a university), and I park literally outside my front office's door. I drive the crappy 2nd car in our family maybe once a month or so to get groceries or something.
For me, the biggest benefit of bike commuting is that I also take recreational rides 3-4-5 times a week at lunch. That'll disappear as the weather cools, but for now it's terrific. On a typical workday, I'll ride about 16 miles between the commute and the lunch ride.
And for me it's not utilitarian — I love riding whenever and wherever I can.