It's hardly such a clear-cut question; there'll be as many reasons as there are people who feel themselves in that position. I can't answer for anyone else, I only know how I feel.
At the age of five, Skagra decided emphatically that God did not exist. This revelation tends to make most people in the universe who have it react in one of two ways - with relief or with despair. Only Skagra responded to it by thinking, 'Wait a second. That means there's a situation vacant.'