Well, after thinking on this some, I believe that what The_Gunslinger658 is saying is that they use race restrictions as a kind of filtering mechanism for potential players.
They believe that disruptive players are more likely to choose non-standard races, so by restricting the game to standard races (human, halfling, elf, dwarf, etc) they filter out a lot of disruptive players right away.
The idea that any one who doesn't want to play a halfling, elf or dwarf is necessarily "disruptive" is both small-minded and oddly elitest.
Quite honestly, a player who wants to play an elf is likely to be the most disruptive.
That whole race is about being a Mary Sue-- just flat out having access to the best stuff, being a subrace that is custom-built to be the most powerful for your class, to have every upside and none of the downside from being immortal and never needing to rest, you are automatically most beautiful than everyone else in the group, you are automatically to be treated as special and superior by all NPCs, particularly any good creatures you might encounter with any special powers and you are automatically liked and loved by anyone you are not meant to kill on sight and will have free access to go whereever you want and do whatever you want for being a member of what the whole world recognizes as the "master race" and the assurance you are absolutely morally superior to everyone else in the world regardless of your actions because it is fundamentally the light skinned elves who define what is good and what is evil (i.e. anything that opposes them or their interests is "evil")
And while progressive interpretations over the editions have scaled a lot of this back from how it has been presented in certain D&D material, in fact-- often enough these days it is very likely that players are going to be treated exactly as human even if their sheet says "elf" and at this point even the 10,000 elf subraces can't really reliably match up to the ability to perfectly tailor your human "racial traits" precisely to fit your class... there is still a certain element of someone choosing "elf" as their race that just utterly stinks of "I want to be vastly superior to all other characters and treated as such at all times we aren't directly referring to the numbers on the sheet."
The elf absolutely should not be a valid PC race option. It really isn't a race so much as an excuse to make a visually young, but ultra competent character with no flaws for whom nothing is a challenge and who is automatically liked and admired by everyone just for being them.
There is nothing interesting or deep or meaningful about that. You aren't taking the base default for human in the world and altering it to create a people who are physically significantly different than the human average and have a significant different society that is different from the base standard human but still realistically functional meaning it has its negative points as much as its positive points-- then considering how an individual with this body type and this society would then be functionally different, what advantages and disadvantages this would confer, what would they be more and less skillful at, and how would they view the world differently... what would be the benefits and drawbacks of being such an individual.
The Elf has NONE of that.They are just "human, but vastly superior in all ways". Simple, basic questions like "how do they get their resources" and "how does their society feed itself" and "who does the labor" are necessarily left entirely unexplored because they couldn't be all perfect morally superior flawless beings who never do any harm and live their whole lives free of responsibility or want in a perfect utopia with every whim provided for if such things ever had to be considered.
There have been some pretty crap excuse for "races" in D&D, things that clearly had little thought put into them or have such little difference from human that they were basically just humans with one extra magical ability or extra body part and that was the beginning and end of it. But at least generally one could see there being some sort of flaw and drawback to the race to counter-balance that. And there have been others where the drive to ensure that they be totally accepted as good guys without question has led to a piss poor exploration of what it would really mean to be that race and how such people would view the world-- but at least in such cases one could possibly go deeper than Wizards did. Yet none of them are quite as absolute unreasonable crap as the Elf race which dates back to before the inception of the game.
The idea that "hey, there was an elf in Lord of the Rings" and thus it was the first race that was added to D&D after it was decided that people need not be only humans. But just because it has been around forever, just because it is "standard" does not mean in anyway it is not far more disruptive than nearly every other race one could come up with would be.
Really, all it actually means is that people have grown so used to not playing Elves as Elves, but rather just acting like humans and the choice of the race just meaning they are taking advantage of the racial benefits to enhance their class... and you as a DM have gotten so very used to utterly ignoring the fact that they are an elf and all the weight being the ultimate super rare master race that all grovel before and is always perfect and considered the standard of morality as they are viewed as practically living gods and favored by all magical creatures... that you don't even really think about it at this point.
But, hey, someone shows up and their character sheet says "Tabaxi" or "Kobold" or "Tiefling" and somehow you have this total melt-down because it is something you aren't accustomed to and thus your brain just can't handle it and you find yourself completely incapable of disregarding it much as you disregard the 3 non-humans (Well, only 2... halflings are just human in every way that matters and their racial traits have always either been a ridiculous, unjustified stretch or are just basic things that would apply equally so to any small person whether they be halfling, goblin, gnome, kobold or fairy.) you are used to disregarding. Somehow you just don't have a breakdown if the player ever reminds you that their character is only 4' tall, but if they dare tell you they have a tail... well, that just ruins the whole damn night, doesn't it?
Seriously, unless the race can literally not even walk on land when that is where the whole adventure takes place or is just too big to fit into the locations you intend the players to go or has special abilities that allow them to just utterly bypass the entire adventure or has special requirements that would require the entire rest of the party make large allowances for them....
I literally cannot imagine how any race could be more disruptive than a player being an elf.
