There are a lot of sticky things to consider when looking at a request for this kind of "option" from the corporate/business angle. One of them is ethics. I know that sounds like it is taking a video game "too seriously" but I am talking for the time being about the business angle of a product (which I assure you, SE takes their product seriously). It is a sticky, possibly ethically questionable, place for a company to put itself to adopt a function that could be seen as endorsing bigotry. Now, before you get all up in arms that I am calling anyone here a bigot for wanting an option, keep reading, because I am most specifically not. What I am pointing out that the code of ethics of many firms/company usually worded against unethical behavior or even behavior that has the appearance of being unethical; it isn't shady but it looks shady, so it is a violation. (/business stuff)
Argument points of saying it is for immersion: not having an option to filter glamours (mind you, the requested option was for a discrete filter: a filter that can be applied per player) is immersive. Again, NOT having the option is more immersive. It is the game as the developers present it is how you maintain immersion. The counter argument to this is that NOT having glamours is also more immersive. But that is almost a separate conversation/argument.
Argument points of saying there are "no reason to not have the option" are false, reasons have been stated and restated, not accepting an argument because it does not agree with your values does not make it invalid. By that token, it could be argued that there is no good reason to implement a filter option. However, I accept that it is genuinely distressing to see some glamours, it's a personally valid argument because it is factual. I do not think it outweighs the cons of implementing the option. The option to "blur" other players? Ok, no, time to play a single player game...
There are NPCs that wear costumes. The tall Fuath in Il Mheg. Adkiragh in Idyllshire. The Lalafell as a race itself are "silly" and cute even compared to Gnomes/Halflings of other games/fantasy franchises. Moogles, don't get me started!!! The silly parts of the Final Fantasy franchise is part of it. If you don't like the silliness than you are playing the wrong game. And I am saying this as a person that doesn't like the costumes (be it moogle, swine, frog, whatever... I dislike them). But I like FF, and that means growing to like the silly. There are glamours I get tired of seeing, but, it's not impacting my game play. If a game isn't supposed to be taken so seriously, why are things like this bothering people so much they want to block it? It's a game, stop taking that Hrothgar in a wedding dress so seriously.
I do use the filter to mute the battle effects for people not in my party. It is purely for the performance of my PC that could use an upgrade. I have suffered to watch many a hunt train kill a mark that wouldn't load on my screen until right before it de-spawned.
I'm all for options (get rid of gender-locks on races AND gear, everything dyeable, viera and hrothgar hair, more variation and options in character creation, the ability to have more options on your character proportions for male and female, some decent beards and facial hair options, some damned eyebrows for highlanders, more variation in character height, an option to include a few options from other races for that "half-elf" life, the ability to glamour DPS armor onto my Tank, or Healer for that battle cleric look, optional secondary arms: like a staff for MNK... etc). There are so many other, game enriching, options that should be a priority for demand than a filter that could put SE in hot water. There is no end of people who love to talk about how modern media is rotting everyone's brains... someone is going to make an issue of it.