There are just means of tailoring a list that don't default to "Because I wrote it down that way ten years ago".
The campaign world being ten years old isn't an excuse either. My setting will be drinking age (US) come March. It's been around for six campaigns, dozens of one-shots, four DMs who were not me, three editions, and two million words of novels. I still don't reject player concepts.
I say 'well for this campaign, let's come up with where you're from, how you got here. It might not show up in future games unless your next character has a hook to the same thing'.
There's no gnomes on Ere, but there were some during the Drunkards& Dinosaurs campaign because someone wanted to play a gnome.
Orcs dying out (aside from living on via minotaurs [long story] and mixed-species children in the form of hobs), but someone wanted to orcs, so it turned out that there are some scattered and isolated orc populations that most people think are myth and whose neighbors have helped hide them from the genocide that wiped them out. The depiction was so good, those guys are canon now.
There are both no elephants on Ere AND I never considered loxodons, but someone wanted to loxodon, so a shipwreck from the 'Here There Be Dragons' part of the map landed one on the coast and they joined the army because people are used to all sort of crazy crap and a weird nose and ears are the least of their problems as long as it's friendly. Wherever they came from is the land of not canon in the rest of the setting, but what's it matter. Dude had fun.
I don't like the dragonborn mechanics and brewed my own dragonsired, but someone (for some reason) wanted to play a dragonborn, so they're a rare 'more human' dragonsired birth where they're more humanand mode-locked into dragon mode.
None of it hurt me. None of it hurt the setting.