I have a scooter, a motorcycle, a car, and 5 bikes. I don't use the car ever, the motorcycle gets used for days when time makes it impossible to ride a bike - maybe once a week if that. I commute on my bike because its the most efficient way too:

1) Create less carbon dioxide
2) Add to my weekly exercise milage.
3) Make me feel good when I get to work
4) See the sights as I pass
5) Because its just plain FUN.

I hate cars. 2 tonne to move 90kg of person? Totally inefficient. If I have my wife, my 2 kids, and luggage as well.. then I tolerate it. Since the price of fuel keeps going up the motorcycle plain costs too much to run. The scooter is so slow I can almost go faster on my mtb so its relegated to parking blocker duty. I ride a cruiser style motorcycle in the winter even if it snows so I figure one of the older mtbs will do fine for that.