I have a few motivators:

1. Health/weight - my commute is long whether I were to ride my bike, take public tansp., or drive (if I had a car). If I don't ride my bike I find by the time I get home I'm to tired & hungry to exercise. It's just easier to make my commute my exercise.

2. Environmental - The main reason I started riding and eventually got rid of my car is the environment.

3. Stress - I hate driving. I am a very mellow person, but one thing that really get's me pissed is dealing with traffic and other cars. When I ride my bike very little bothers me.