Because he want to wake up some day as America's First Dictator.
or
Because the teacher said it was a piece of cake!
or
1,000,001: One to change the bulb and 1,000,000 to rebuild civilization to the point where they need light bulbs again.
or
It held up a pair of pants.
or
None. They will never find a bulb that burns as brightly as the old one.
or