In my experience it's more like "because I am uncomfortable with the idea that we have no purpose, there is no afterlife, and children die of cancer for no reason."
Atheists don't claim that there are no gods. It's is impossible to prove the non-existence of something, so if you make such a claim, you get into belief territory. Most atheists are agnostic atheists, i.e. I'll be happy to believe in your gods once you present evidence for their existence.