So we don't have enough devs

[Airget]

And also the fact that most of the money goes to their (SE) other projects, only small portion is allocated to FFXIV
Part of business i suppose..

FFXIV survived because SE allocated more funds into the game to give it a second chance, so it wouldn't make sense to invest more money only to have that money go to the game. It also wouldn't make sense to make an MMO and just throw all funds back into the game, that just defeats the purpose of the business.

It's possible FFXIV won't always divert so much funds to other games, but until they pay off their tab they have no choice but to use the profit to payback into the cost of making/remaking the game.