I've noticed that a very common argument in favor of atheism is that you don't NEED a God to explain the universe, or life: you can point to the Big Bang,and evolution. But, I'm curious what atheists think about a God who created the universe via the Big Bang and thereby ultimately created life via evolution (because life evolved inside the universe). This kind of God is consistent with all the scientific theories about how the universe and life formed. This kind of God is not a "scientific question" because there is no way to measure or prove for or against this God's existence, because She/He is entirely outside the realm of science, being outside of the universe. Science ONLY deals with the natural world (e.g., what the universe was like at the very beginning just after the Big Bang, or how organic molecules may have formed spontaneously on the early earth.) Science does not deal with things that happened before the Big Bang because they are not measurable. Also, this kind of God could still do miracles, but that itself cannot be proven without the opportunity to personally experience a miracle and have the proper observing capabilities or equipment on hand - that's not a scientific discussion, it's just an "experiences discussion" between between people who feel that they've experienced miracles (myself included) versus people who have never experienced miracles.
I also know there's an "occam's razor" argument saying "well if we don't need God to explain life or the universe, it's simpler for any God not to exist and therefore God must not exist" but I don't actually think it's "simpler" to say that the universe came out of nothing, rather than "something." (But, again, I can't prove it - it's just my personal opinion that "some cause" is simpler than "no cause". Not a scientific question.) Also, people often treat Occam's razor like it's some kind of universal truth, when it's really not...there are a lot of cases where things in reality are more complicated than they need to be, and more complicated than the "simplest" solution.
Anyway, I'm basically just wondering what the fundamental underlying reason is that atheists don't believe in a god when the god is defined this way, completely consistently with humanity's scientific discoveries so far, and completely out of the realm of science (after all, I'm not familiar with any religious text that says God should be scientifically "provable" on a worldwide scale; there's a lot more stuff about the "mystery of God" and God acting on the scale of individual people's lives). Does it all ultimately boil down to the issue of "no personal experience with miracle --> no gods exist as far I can tell"?