Here's an example: take your standard fantasy #rpg setting, with humans, elves, dwarves, orcs, giants, dragons, whatever other sophonts you may have. Remove the "humans". How does that change things?
I feel like I'd be fine with it. I've been in some campaigns where there was a 'humans only' limitation, and it felt like part of the fantasy was just missing. Sometimes half the fun of escapism is being something other than human.
Also, I feel like a 'no humans' anywhere limit would help to build an attitude of racial equality, since there's no humans in the world to have as a baseline for comparison.
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