What leads you to believe that all evolutionists are atheists? Isn't that a rather general statement that would be impossible to verify?
Perhaps you missed the sarcasm tag. Perhaps it's because of the many times creationists have called me an atheist despite knowing nothing more about me than that I believe that the theory of evolution provides the best explanation for observed facts. I am not an atheist, so I don't believe that all evolutionists are atheists, since I am a counterexample. However, that is the belief of many creationists.