It's a simple question! You may have supposed, like I always did, it had something to do with Square's propensity for giving everything a stupid, stupid name. If you did, well, we're both wrong.
While some of you may already know the story behind this, the name actually makes sense. Shocking, no? Here's a portion of a little interview Wired held with series composer Nobuo Uematsu:
Is it true, I asked, that the game is called Final Fantasy because Sakaguchi was going to go back to college and quit the game biz? Uematsu laughed: It's true that Sakaguchi was going to quit, he said, but the bigger reason, the real reason, was that Square was going to go bankrupt and the designers believed that it would be the company's swan song.
So there was never meant to be a Final Fantasy II, let alone a Final Fantasy XIV. So Square, for that, you're off the hook. But Infinite Undiscovery, well, for that, no excuses.