I can't speak for the others, but for myself, I sorely notice the change in the ingame population. When you see only the same players run by you everytime you play, all of them living in the bubble that is their hardcore endgame linkshell, and close to no new blood entering the game...
Well, it simply doesn't feel like the ffxiv it used to be, despite all the flaws that was a fact back then. The game has improved so much by now, that the development itself promises nothing but a bright future for the game. But with no players left to play with, it all feels... empty.

And of course one could easily move on to another mmo, but the fact is, I like this game! I like this fictive world, its lore, its music etc. And I liked the experiences I had months back with fellow players. And with so much potential being inserted into this game with every patch, I really want to experience it again.

That is why I care so much, why I really want the game to be more popular than it currently is, and why I won't leave it behind for another mmo just like that.