None. They just let Marketing explain that "Dead Bulb" is a feature.
or
Because all the fans left!
or
The ceremony was rubbish - but the reception was brilliant.
or
Three:
One to write the light bulb removal program,
one to write the light bulb insertion program, and
one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
or