Because of a finite c...
...if some idiot engineer somewhere in the cosmos figures out how to fracture space-time, creating a light-speed expanding bubble of nothingness that will eventually swallow the entire universe, none of the other inhabitants will have any idea what has happened, even after the edge of the bubble intersects them.
Somehow, I find that a comforting thought, and I can wish those guys at the Large Hadron Collider the best of luck with a clear conscience. I'm not afraid of death, as long as it happens in my sleep.