or
Because there's no one else to wag it for him.
or
Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes (knowing that it's already burned out).
or
Fifty — one to screw in the bulb and 49 to guard him/her.
or
Nearly unanswerable, since the one who tries to change it usually drops it, and the others call for a planning session.
or