God and religion are simply collections of the stuff that is unknowable. For whatever reasons people develop relationships with this unknowable stuff. For some it provides answers or comfort or guidance.
What happens when we die? An unknowable question that bothers some people. For comfort, they turn to an unknowable collection of stories they call God that tells them not to worry heaven is waiting.
That's fine. That's their prerogative. Other people, however see no value in spending too much time on the unknowable (whether questions or the illusions of answers).
And of course over time many of the things that were once unknowable become known. Lighting doesn't come from Zeus, for instance. As what we know grows, what we don't know shrinks and God beliefs start to fall apart or simply morph/shift into new collections of the unknown.
People sometimes ask the question, if God showed up in front of you, would you then believe. Well, no, if he was there in front of me than he would no longer be unknowable and so wouldn't be God, he would just be some dude standing in front of me with cosmic powers.
With that being said I do not consider myself an atheist or an agnostic. No decision "not to believe" is necessary, nor does it require any sort of grand struggle of logic or philosophy. My spiritual existence is not defined or undefined by someone else's beliefs.