The very fact that we're having this conversation means there's more to the story than "nothing." You're being obtuse. A lack of belief, while living in a society that expects it, becomes something notable, and that notability is more than nothing. Just like being bald is only notable in a world where hair is expected, being atheist in a world where beliefs are expected is notable. Being notable is a societal tangible thing, even if "not believing" would otherwise not be for any other topic. Being atheist would be as empty as you're describing if we as a people didn't talk about religion, but in reality we do, so it carries weight, which affects behavior.