All of them wear glasses without any visible means of support. The first one is even the focus of a quest to get her some new glasses.
OK, so if I'm prepared to accept that the world of Eorzea has dragons, so why is its treatment of spectacle-wearing cats worth mentioning?
Well, just because a world has dragons, that doesn't mean anything goes.
When you play a game or read a novel or watch a movie, you are entering a world of fiction. There are truths about the world depicted that are not true of the world we live in, Reality. You are a medieval general. Sherlock Holmes is a person. A mother and daughter are looking for love. The fiction of the game, novel or movie constitutes the premise you have to accept if you're to invest yourself in its world.
What about everything the fiction doesn't describe, though? Well, as I've said, it defaults to how it is in Reality. Horses can't shoot arrows. Queen Victoria was a person. People live in the United States of America.
So far, so good.
What about things that neither the fiction nor the defaults of Reality describe? Arrows fly further than they should. Watson limps in the wrong leg. Germans speak English to each other.
Obviously, we do know why this is the way things are. Longer-range arrows make for better gameplay . Watson limps in the wrong leg because Arthur Conan Doyle forgot in which one he'd previously said he was wounded. An English-speaking audience won't necessarily comprehend a conversation in German. They're there for reasons outside the context of the fictional world: the fiction itself is an artefact of Reality.
Although such incongruities may well be understandable, they're somehow unsatisfactory. This is because they poke holes in the fabric of the fictional world. We can't buy into them; we simply have to accept them and move on. This makes the situation less than ideal.
The reason that everything the fiction omits defaults to the way Reality does it is that we have an understanding of Reality. We need to be able to make rational deductions about what will happen if we do this or that, or what must have happened for things to be like that or this, and unless the fiction tells us otherwise we defer to Reality.
This is true of any work of fiction.
Suppose we're reading a novel. We're following a story: we want to be able to think about why things have happened and what that means for what will happen. This requires us to have an operational model of the fictional world. Without one, we can't establish hypotheses or make inferences. In the 2010 TV series Sherlock, Watson's change of leg to limp in is found to be psychosomatic as a result of post-traumatic stress (he was in the army), so placing it nicely within the fiction. As a result, the next time we see something seemingly at odds with the fiction, we can feel more confident that there'll be an in-fiction explanation rather than an out-of-fiction one.
This raises the issue of trust. When you have a good game designer, or a good novelist, or a good director, you can trust that what happens happens because it fits the fiction. If the enemy doesn't advance its forces, then it's waiting for support from its allies, not because of bad AI. If a boy hugs himself while being asked questions then he's afraid, it's not just a bit of acting business to slow down the pacing. If the grandmother starts to lose weight, it's because she's developing a terminal illness, not because the actress has changed her personal trainer.
In the early days of virtual world development, we called this concept "realisticness". A better word would be "verisimilitude", but realisticness was preferred because it tended to be used in the negative: concepts were said to be "unrealistic" if what happened didn't match the player's understand of what "should" happen. If I drop a hedgehog off a tall cliff, the hedgehog should die. My character dies when I fall off that cliff: so should the hedgehog. The hedgehog doesn't die, though. That's unrealistic.
If the hedgehog had previously been flagged as being magical, OK, well you might feel able to cut it some slack. If it appears to be just a regular hedgehog, though? Well, in a game that you feel you can trust, the reason it doesn't die is perhaps because it really is magical despite looking ordinary, so its survival gives you information about the creature that you didn't previously have and which you can later perhaps exploit. You would feel justified in exploring this possibility, and so be somewhat disappointed if you discovered that it is indeed just a nothing-special hedgehog that ought to die when tossed from a cliff but doesn't.
You can also get unrealisticness when the fiction doesn't hold. I've just melted a hole through a castle wall with this wand: why can't I use it to negotiate this insurmountable waist-high fence? Yes, I know than in Reality I can't do much damage to a fence using a stick, but this one can melt holes in walls so it ought to be able to remove a less substantial obstacle with relative ease.
When something is unrealistic, then, it means there's an inconsistency. Either the fiction has failed or the non-fiction has failed and the fiction can't cover the failure. In both cases it's bad fiction, and this is why people don't like it: their model of the made-up world is being broken for no good reason and their theories about what might happen next are now worthless .
The reason, then, that Miqo'te glasses-wearing is problematic but the existence of dragons isn't, is that the fiction explains the dragons but it's silent on the subject of gravity-defying spectacles.
There are several reasonable reponses that could be provided to explain this away. "They have side ridges you can't see because of their hair"; "gosh, we hadn't noticed that, thanks, we'll give them all lunettes from now on"; "yes, they shouldn't be able to wear them that way but we need to re-use the art assets". It would not, however, be reasonable to respond "why are you saying that glasses-wearing cat people are unrealistic when cat people themselves are unrealistic?". This is because we know the answer: the Miqo'te, like the dragons, are covered by the fiction, but the spectacle positioning doesn't seem to be. If the fiction addressed the issue, the glasses couldn't said to be unrealistic.
This point is important, because (as I said) it's all about trust. In the Game of Thrones TV series, there's a sequence in season 7, episode 6 (Beyond the Wall ), in which the character Jon Snow falls into water through broken ice and is utterly drenched through, yet he drags himself out into the polar conditions without any ill effects.
Realistically, Jon should have hypothermia, yet he doesn't. OK, so why doesn't he? Well, if I can trust the fiction, it's telling me something. Maybe his sword is magically protecting him? Maybe he has an innate ability to resist cold that mirrors the one Daenerys Targaryen has to resist heat? Maybe something as-yet-unknown warmed the water? All these hypotheses have interesting implications. However, if the reason he doesn't suffer is that he's wearing plot armour, frankly this isn't good enough. It's effectively saying "don't worry your pretty head about it, audience dear, just accept it like you accept the dragons". The point is, if I did accept it like I accept the dragons, then his survival should mean something special: the dragons are something special.
So it is with Final Fantasy XIV, but in a more productive way. In the great scheme of things, of course it's not important that Miqo'te wear their glasses the same way as Arthur out of the cartoon series Arthur. This is a whimsical world which at times goes out of its way to acknowledge how bonkers it is. That's kind of the point, though. Little examples such as this serve to reinforce the idea that you can't actually trust everything all of the time; on occasion, you simply have to go with the flow. In other words, it's establishing the principle that the game world isn't realistic, and that you can expect minor plot holes and inconsitencies from time to time. It's being honest with the player, which is rather refreshing.
Realisticness matters, but if you don't have it then that can tell you something about the virtual world, too.