This is a good point. I would think the reason most DM's primary focus is on the other civilized areas, is because they don't want to run evil campaigns. That's true for most D&D games I know.
If you are discussing a coherent world, you can have these other empires exist. They can trade with one another. And they also enslave others. Heck, your top four are probably the biggest slavers in FR if you stick to traditional lore. If you make the elves and dwarves and humans and tabaxi and dragonborn and gnomes follow the typical societal norms that we think of, and that most DM's apply, such as killing can be punished, then those other empires are recessed in the world. They are subverts. They work underground and in the darkness. If you have a group of PC's, and most are good, they are the light that might come across these empires.
Now, if you have an evil campaign (and again, you are just using traditional lore of drow are mostly bad, etc), then odds are you start your campaign in one of these places. But, like I said, there are probably more good campaigns than evil.
Lastly, I don't believe most DM's have this many empires. I know some that have, and it bothered me. The game was still fun, but I sometimes found myself refocusing on the fun and players and enjoyment rather than the messed up logic.
I don't get what playing in a good or evil campaign has to do with anything.
Unless you are saying that they don't start in the area, so they don't bother even thinking about it, but in that case why are such DMs so adamant about the vision for their world?
"My world must fit my vision, but since we are starting in Kalay, I'm not going to bother designing or thinking about anything not directly connected to Kalay and the party"
Personally, I wonder if your answer highlights exactly what I'm talking about, since it seems that building the world that the PCs aren't interacting with and may never interact with doesn't seem to even occur to you as what I was discussing.
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The core books are the beginning, not the end.
I think that you probably should reflect on the fact that it is now evident that your play expectations and experience are quite different than that of other people you are conversing with, and perhaps you might wish to refrain from prescriptive comments about how people should run their games or build their worlds
Why does this always get so confrontational? Why are players seeking to add to a world, to build their own visions being treated like they are spweing silly string all over the Louvre?
The question asked at the beginning was "Why do people want to play something other than the core four" and your response here, to a person saying "hey, when discussing DnD as a whole, the PHB is a good list of agreed upon options." is that
they should reflect on how
their game expeirence is not universal and that they should not prescribe on how others run the worlds they build.
And, they did nothing of the sort. They just said that as a discussion of DnD as a whole, starting from the PHB seems like a fair starting point.
But you... you seem to insist on taking on the role of a beleaguered artist. How dare we plebian players demand of the DM who works so hard and does so much? And I'm tired, so maybe I'm being provocative and snappy, but so many DMs on this thread, who are arguing that the world's shouldn't include these races that the players want to play, they are treating the player like a nuisance, instead of a partner.
Look, I don't say yes to every idea my players come up with. I had one guy who wanted to play an immortal paladin who lost his powers and was forced to consume the souls of those he slayed as a weapon of the gods. And I told him, "man, we are starting at level 1, that is way too powerful of a concept. Maybe a different time, but that won't work here."
But I also had a young lady who thought that Tieflings were cool. And I had never put tielfings in that particular world, so we decided that since she was joining in the middle of a Fey dungeon, that she was the a last surviving tiefling, taken in by the Fey. And she was one of the best players and characters I have had the joy of running for.
Maybe you think compromise is a dirty word, a word that ruins your world and forces more burdens on your back. Maybe you don't and my exhaustion is making me unreasonably snappy. But I don't get this antagonism. Your players are not greedy children with grubby hands that need to be monitored lest they smudge the fine china. They are your partners. And if you are sick of doing the Lion's share of the work, or feel like doing more work for the sake of your partners isn't worth it, they are the ones who can help you.
A lot of the people in these threads are old enough to know how a partnership works. And maybe that is exactly how you run your tables, but there are an awful lot of comments over the last few pages that seem to be painting players with passionate ideas as a problem to be dealt with.