They tend to be the newly-hatched atheists. The ones who recently had their eyes opened and feel the urge to show off. It usually tapers off once they find their feet and hit their stride, but not always.
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.'