I personally believe it's a matter of belief and faith. In other words, just the same as it exists for every other denomination of faith. Just as there is no concrete evidence to support the existence of one or more deities, neither is there evidence to refute the existence of one. And so, atheism refutes the existence of deities while religion supports the existence of higher beings.I suppose I have a question- why exactly are people atheists as opposed to agnostics? From what I can tell, the basis for most atheists being atheists is logical/scientific- i.e., "there is no proof of God therefore I do not believe in him." However, isn't it true that there might be the tiniest chance that God does, in fact, exist? Scientific facts are not in truth facts, but rather a statement that "we're 99% sure this is the way it is." Doesn't this mean that a modified version of Pascal's Wager effectively states agnosticism is superior to atheism, since we can never be 100% sure God doesn't exist? Sorry if I phrased anything offensively, I didn't mean to; I was just curious.
The entire notion of atheism, as far as I'm concerned, is that individuals cannot believe in something or force themselves to believe in something that simply does not make sense to them. Atheism is rooted in the logic of the world as we currently understand it, although that doesn't really say much.