As the prefix indicates, atheism is the absence of belief in God rather than the belief that God does not exist. It’s therefore not contradictory to be an atheist and to be open to proof of the existence of God or anything else should it ever come along. It’s simply rational.
Article on this aspect of atheism.
Being an atheist has its comforts. When bad things happen to good people, you don’t have to look for a reason why. You just have to help them deal with whatever random misfortune has befallen them. You also don’t need any motivation beyond basic human sympathy for doing so (or enlightened self-interest if you’re cynical). Whatever I do in life I don’t expect eternal life as a reward, so I have to do the best I can while I’m alive.