@Crimson Longinus , just to note with your example - doing something like denying a elf in an Asian campaign depends on the world itself. For example, you could drop an elf in Karu-Tur, as that's based on the eastern half of Faerun - so they could be either native to, say Shou Lung or have traveled/migrated there. Rokugan? Maybe not so much.
Sometimes, it can be an issue if the the DM has defined the world narrowly before they've invited players to discuss the campaign - the world is set before the players have a chance to put in their input. It may be that the campaign world has been around for a while from previous games or they've just done a lot of prep before adding in the PCs. If everyone's on board with any restrictions, there (probably) won't be any friction. The keeping Klingons out of a Star Trek game because everyone wants to stay true to the source material makes sense in that example.
But if the DM comes at the players as "this is the way it will be", they're possibly cutting themselves off from some possibly interesting story ideas or creating friction with the players by limiting their imagination. The Millenium Falcon flies out of the Borg Cube in First Contact (ala escaping the Death Star II from RotJ), so some groups
might find it fun to slip a Klingon in as a Hutt bodyguard and run with it.
As before, I'm not immune to being somewhat rigid - before my homebrew Amberos was ever introduced to my play group, I'd done a whole continent map, written a book(let) on all the various countries and even gone through the MM and chosen areas where certain monsters/races could be found.
It caused me a lot of strife in later editions as new races and monsters sometimes hadn't even been considered and thus had "no place" if I stuck to my guns, even if I overall liked the new content (case in point: Dragonborn - luckily, in the end I had a similar monstrous race I could riff off of, allowing me to slot the race in for PC use).
The main point is, sometimes let your guard down and try something out of the ordinary. You might like the results.