I respectfully disagree, because it is just as reasonable that a God exists as that God does not exist, maybe even more reasonable.
Are you sure? Is it just as reasonable to believe that an Invisible Pink Unicorn exists as to believe it does not? I can see no reason that would be any different.
But the reason that you don't believe an Invisible Pink Unicorn exists is because there's never been any evidence for such a thing, and nobody ever tried to convince you of it anyway, so you dismiss the idea. For exactly the same reasons that I dismiss the idea of God.
I think the actual main cause of atheism is unwillingness to look at and/or inability to see the evidence for the existence of God. A secondary cause is lack of interest. If one does not think they need God, why bother to look?
You would be wrong on both counts: theists have been trying to show some sort of "evidence" for God since they first dreamed up the idea of God, and so far have come up with nothing that any rationale person would call "evidence," as some theists have even asserted in this very thread.
But second, I ask you, if you thought think that you
need God for something, how could you ever suppose that it was God, not happenstance, that provided it? Because here's another truth for you to process: many people who believe in God, and
need God, have their needs relentlessly ignored. I would even go so far as to suggest that they are in the very, very large majority.
Do you know what I think it is that theologians and priests are actually good at? It's the art of explaining why things never turn out the way that their theology suggests it ought to. Why the prayers and sacrifices didn't bring rain, or why God didn't save the life of one child, while another lived, and that sort of thing.