See my other comment in this thread:

But you can say with reasonable certainty that there is probably no god, because the existence of god conflicts with some of our more useful models of the universe, like natural laws and reproducibility. Reproducibility is the foundation of scientific understanding, and if a "god" existed that could bend the universe to his will or grant mortals the power to perform miracles, reproducibility would just be an illusion and our scientific understanding of the universe would be meaningless. So then we choose, which has served us better? The idea that the supernatural and higher powers might exist, or science?

This is the point a lot of atheists arrive at whether they realize it consciously or not, they understand that the supernatural is fundamentally incompatible with our scientific understanding of the universe. Because our scientific understanding and all of its applications have served us so well, rejecting the supernatural becomes a no-brainer. It's not even a conscious decision, we simply can no longer understand how god and miracles can possibly exist within the framework of a universe in which science can know the laws of physics and space and time.

So then it becomes an issue. Why are we even talking about this in the first place? Why don't reasonable people simply put these notions aside as unsubstantiated and worse, not particularly useful? You can argue that historically, religious discussions were useful, because the output from these were ethical and moral conclusions, which had social justice and policy applications. But our justice code has been secular (for the most part) for centuries now. We have an understanding of ethics and public health and welfare that is based on scientific data and secular humanist values. There really is no need to discuss religion now, except it remains this thing that needs to be constantly dealt with. Thus the source of atheist frustration. We don't need it, yet we can't get rid of it.