If there is a creator, and it is a creator that interferes in human affairs, these interferences would be measurable. If it does not interfere, who cares if it exists or not, since there is no way to measure it, and we do not know what its intentions are since there are no measurements, it seems futile to randomly guess.
Then there is Occam's razor - We know there is a Universe, we perceive it. To suppose that the existence of the Universe is predicated on the existence of a creator, we can also make the supposition that the creator needs a creator, and that creator a creator, ad infinitum. It seems much more reasonable, to base our understandings of the universe on things which we do know.