Not trolling here, just my opinion.
It's probably because as soon as you put "final" and "fantasy" onto something, it sells like crazy (ecept for the first movie lol).
Ever since the last director left the company most of the newer FFs lost their substances (as do most of the game they make now), that's why they keep doing remake OR sequel to already popular ones (like all the retconing they did with FF7). It's a good thing Enix is still publishing Tri-Ace's stuff IMO