Some more zealous atheists get the idea that the existence or non-existence of God is the end-all-be-all of religious faith. I was at a class taught by a Buddhist monk, and someone asked him about his beliefs in terms of the more mystical aspects of Buddhism, like believing in beings like Devas, and he said something that really stuck with me. I don't remember his exact words, but the gist was "well, when I took my vows and became a monk, part of that meant that yes, I do believe in things like Devas, because that's just part of the package. But the truth is that it doesn't really matter if Devas exist - that's not what it's about." To him, the existence of Buddhist mythical beings was one of the least important parts of his faith - it was just something that came as part of the package.
Religion and spirituality have a million effects on the people who practice them, and on the world - very few of which really depend on the existence or non-existence of God or Gods. The important question isn't "does God exist?" - the question is "what effect does believing in my religion have on me, and on the people in my life?"