You're using a definition of "atheism" that applies to nobody. In my experience, most people who call themselves atheists believe that there is no evidence that a god or gods exist and therefore disbelief is the only logical course of action. We are open, in theory, to the very remote chance we are wrong, but don't like to call ourselves "agnostic" because that seems to lend too much credence to the idea that there may be a god, which we view as fantastically unlikely.