I've always restricted PC races for thematic purposes. In my recent campaign I limited the PC races to humans, elves, and half-elves because I wanted to focus on a very narrow part of Greyhawk during the Greyhawk wars. Doing this allowed me to mold the other NPC races, casting them in a less than favorable light. Dwarves became greedy cowards and merchants who played both sides off each other in the wars, arming orcs and humans alike. Gnome were more fey than humanoid, living in the Fading Lands between Oerth and the Feywild. Halflings were more like Old Gaffer than Frodo or Bilbo. Humans were brash, bold, and either seeking power or trying to prevent tyranny. In fact, every land but elven lands were more tyrannical. The Elves got a full treatment of every positive spin I could muster. Only Drow had some tyrants and traitors. Lolth was elevated to a black sheep of the Pantheon. I enjoyed this very different take on the PC races and I'd happily do it again.
In the world I am creating, Variant Humans are not an option at my table. Not because I have anything against them, but for two specific reasons.
1. All characters in my world will begin with a feat at level one.
2. They have been replaced by the Munthreks (Draconic word for humans) that are more draconic then the standard human.
In my group's D&D multiverse, humans were hunted to near extinction by Asmodeus as part of a deal with Fraz-urb'luu to allow the Arch-Fiend to freely travel through the various material planes to do whatever he wished (long story). Sora (one of my previous characters reborn into the old dragon god Io) brought all the humans to a special plane where they could be safe from the Arch-fiend, as only she could permit travel into and out of the plane, until Asmodues was dealt with. Since the plane was controlled by her and her raw draconic magic, all humans were subtly imbued with draconic energy. Standard humans are those who show no real signs of draconic influence while Munthreks are humans that manifest certain draconic traits like scales, horns, claws, limited flight, innate magic and so on. I'm building them like the Simic Hybrid so players can customize what kind of draconic traits their characters can have.
Only setting specific stuff I can't jam in somewhere. So, Kender, Kalasthar and Simic Hybrids
If someone really wants to be a Kender or Kalasthar the like then I guess I can jam them somewhere, but Kender are Kender and Kalasthar are very Eberron tied. You wanna be a Simic Hybrid? Well, roll for fleshcrafting yourself into a fish monster and we'll see how it goes, but that's more a 'semi-unique thing you've done to yourself' and not a full on race
I haven't barred people from playing them, but I did remove halflings, dwarves and gnomes from my world since I find all of them really boring. (Sorry. To me they're just short human, short wide human, and short wacky human.) It's not that I think they're bad, it's just that I don't care about them, so I didn't want to make a default place for them. I'd still let somebody play one if they wanted, but it would be up to the player to tell me what they are and where it would fit.
Half-orcs and half-elves are a hard no though; they're just elves and orcs, lest we endorse the idea that some races are "true" races and others are "mixed" and all the creepy weird racism bound up in that. In my world almost every living humanoid can interbreed, so rather than make a big list of hybrid "races" the policy is that you pick the mechanical package that represents your character best, and I don't care which of your parents had pointy ears.
As for who I made wildly different, my kobolds have almost no dragon in them and aren't very humanoid; they're made of equal parts dog and lizard, on a very ferrety body. Culturally they have a lot of proud warrior stuff going on, but they also come up a lot as weirdo inventor types, since tunneling extensively underground means they're the people who most often find the pre-apocalypse magitech relics.
Also my goblins are round and hairy, with a pronounced underbite, comically short limbs, big frantic eyes and sort of batty ears right at the tops of their heads. They're misunderstood rather than evil; mostly they're just trash-eating communists who don't see an issue with taking what's not being used. Kind of D&D wombles.
Oh right, and the eladrin aren't really of fey origin, they just did a massive ritual one time trying to steal immortality from the feywild. It didn't exactly work, but it did let them come back millennia later and colonise the elves under the pretence of being "cousins".
In Yoon Suin, there are only human, dwarves, slugmen and crabmen. If you are local that is. If you're an outsider, you can be another race. But beware - someone might decide your blood is a good ingredient for magic.