Obvious reason being Square-Enix, they've injected FF into just about every other game they've (or their individual portions prior to the merger) ever created over the last decade or so, aside from a few (such as my favorite non-FF title of theirs, The Bouncer).
It's a similar concept to various other VG companies injecting characters from their equally/more-so popular franchises into other games for fun and flair, like how Nintendo threw just about every Mario and Kirby reference it could into LoZ Link's Awakening. It happens, you eventually learn to just enjoy it and have fun with the game and its endless cross-franchising shenanigans XD