None. The light bulb contains the seeds of its own revolution.
or
Because it gave him a big wave!
or
None, because people who glow in the dark don't need light bulbs.
Note: Topical to the Chernobyl Reactor disaster of 1984.
or
The owner got tired of the (w)hole business!
or
The price of bacon would go up.
or
It was like love meant nothing to her.
or
Because he was feeling crumby.
or