"all atheists" is too big a category. There are many atheists I disagree with.
Let me follow my pattern of eluding a poorly worded question by asking a different question: what did people have faith in before the emergence of monotheisms?
Just to piggyback on this a little, I usually don't see religion and lack thereof the same way as other atheists I encounter. In fact (maybe I'm a dick) I often categorize other atheists as "angry at God atheists." They generally come from a religious background and at some point feel like if God were real things wouldn't be the way they are, so now they claim to be atheists. They're the ones I assume will go back to God at some point in their life, like when their SO tells them to, or when they have kids, or when they suffer a significant loss or fear death.
More often than not I do not call myself an atheist. I really don't want to be thrown in with the majority of that community. But I also don't want the title to lead anyone to think that I believe I know anything about the existence or lack of existence of any sort of God. Just as has been pointed out in any debate about the existence of God that has gone on for more than two minutes, you can't prove a negative. So for me any claim has to first be substantiated before it can be considered. The claim that God exists is completely unsubstantiated and therefore I do not give it any consideration. So I'm not making any claim of knowledge about God's existence. He doesn't get that special attention. Supernatural beings of all sorts fall into the same category. They violate the laws of reality as far as can be determined so they are impossible in my view. It requires some sort of evidence that such a thing is even possible before I would consider the existence of God more seriously than I would consider the existence of the Flying Spaghetti Monster.
I do not come from a religious background. I have never in my life been taught or believed that God existed. I think that is a pretty fundamental difference in the way I approach this. Atheism is not a form of rebellion for me. I am not rejecting my parents, nor my upbringing or my community by declaring my atheism.
Faith in the supernatural is an odd thing to me. Very, very odd. I get that most the people around me participate, but it simply doesn't make any sense to me.