@Kanye-Qwest That seems like a bit of an excessive and unwarranted response, you know.
And it's not just pedantics, either. It's important for a roleplaying setting (yes, even a fantasy setting set in a non-Earth world) to have some sense of cultural realism and weight to it, not just to unrustle people's jimmies, but also to facilitate actually playing in that world. And the more arbitrary unrealities that you set in a world, the less possible it is for people to play in that world, at least without trying to wrap their mind around some fundamentally alien viewpoints. And no, cultural unrealities aren't the same thing as fantastical unrealities - it's a lot easier to accept a world like the world we know, but with magic, than it is to accept a world like the world we know, that somehow lacks, say, marriage as a societal construct. The latter is going to cause /even people who like and want your game to succeed/ to recoil a bit, especially if the premise is "this world is a lot like the world you know, except that no one has ever thought about getting married or spending their lives with just one person in a faithful romantic/domestic relationship".
It's one of the reasons that I don't play Pern games, and often recoiled from Pern as a setting, even if some elements were cool. Dragons? Fine. Time travel and teleportation? Cool. A setting filled with humans without any sort of /religion/? That's just bizarre. And I say that as an atheist. (And yes, there are other bizarre and ill-thought-out bits of that setting, that's just the one that gets me /every time I think about it/, because it flies in the face of what we know about human beings in a weird and gratuitous sort of way.) At the same time, McCaffery's other works, which have just as little religiosity in them, for the most part, but take place in universes where religion exists but is just never talked about or factors into plots or personalities of protagonists? Don't bother me as much. Because the idea is not so much "I want to play a super religious PC and have all my characterization revolve around religion" as it is, "I want to know that human beings in this setting work in approximately the same ways as they work in real life, so that I can play my character appropriate and interact with other characters in appropriate and genuine ways".
Although, for that matter, just admitting that something is arbitrary, and not having a meltdown every time someone points out that it's weird and arbitrary is fine, too. I've run evil campaigns where I've said up front, "Yes, you're playing evil. It's going to be four-color evil, with grand schemes, betrayals, and Taking Over the World, not war crimes and torture, even if your character is written as to not have any problems with those. We're just not going to do it." And then all you have to do whenever it comes up is, "Yep, it's a bit weird, but it facilitates the game we want to play." And say nothing more about it. Because that at least acknowledges the unreality of it - and, as an aside, established the GM as an adult who knows it's unrealistic and is totally okay with that being pointed out, but is just setting parameters for the game, not feeling the urge to start temper tantruming at people for being bewildered.