I you believe gods
can exists, but the beings that call themselves gods are false...then what constitutes a god? Is it nothing less than complete omniscience and omnipotence? Seems like they want Abrahamic goal posts. It takes a lot of spice out of pantheism and dispersed portfolios. (This is why I've never like Ao. I consider him a bad development in FR lore. I mean A-lpha, O-mega? C'mon).
The strain of "atheism" that is usually expressed by PCs in my games is that, essentially, gods are just powerful beings with good PR and only deserve worship in a transactional sense. At my most cynical I think those players just balk at the idea of any spiritual system where they are accountable to a being that has dominion over them. It stirs all sorts of emotions about institutional power, so they'd rather invalidate it though some carefully plucked determinism.
In most games they're right, since gods seem only to express their will through those they give spells to (does prayer benefit the commoner NPC? Can blasphemy spiritually endanger an atheist PC? Are holy cities actually protected by their patron gods?) Almost every player I've met also assumes the
Gods Need Prayer Badly (TV tropes link) framework in fantasy unless it's been specifically stated otherwise. It's pervasive, human-centric and pretty egotistical. But it's an idea that makes atheism seem like a safe choice.
