I can only speak for myself, but it's mostly for the entertainment value. The entertainment of "good" questions to ponder, demonstrating "flaws" in reasoning (usually with theists but sometimes atheists), sharing my perspective, seeing other people's perspectives. For example, you are an agnostic and at one point I had to ask myself why I was not an agnostic versus an atheist. Back then it was not like a knew for a fact that Gods didn't exist, I simply found the claim magical and unbelievable. This led to what is the difference between being agnostic of magical super Beings and magical fairies? The answer was nothing other than people not claiming magical fairies to be real. I love "good" reasoning because it's a form of problem/puzzle solving. I realized I needed "good" reasoning to support the "real" possibility of Gods before I could "reasonably" be agnostic of the concept. Life on this planet is evidence for the "real" possibility of other life to be "reasonably" agnostic about. Being an atheist covers both being skeptical of the claim but still open for any evidence and or reasoning that could shine a light of validity to the claims of Gods/Goddesses. Atheism is the only position to be if you have nothing to move towards agnosticism and even further to theism. Agnosticism and theisms both need support from evidence and or reasoning and when nothing can "yet" be had, atheism is the only reasonable conclusion. It was an entertaining process for me to conclude this and maybe now that you have seen my reasoning, you might consider agnosticism to be an irrational position if you cannot find "good" reasoning for the "real" possibility vs. the "imagined" possibility that most agnostics share.