a. To stop middle age spread
b. To flip my finger at people flying occupied aircraft into occupied buildings.
c. To say "tee-hee, suckers" at Friday night traffic.
d. To maintain "Mommy is badazz" reputation with my teenagers.

As far as whole "green" thing goes - pffffttttt! Due to my professional training I am saving Mother Earth at my desk 9 to 5, five days a week.