>>718110657
Because Square Enix's business side is labyrinthian horesehit and pretty much handles every numbered Final Fantasy as if they were separate IPs. And even when you DO get the rights to reference one game, there's even more bullshit just to get individual things like music and fucking art, as evidenced by how splintered VII's content in Smash was. Crazy reminder that Cloud couldn't even have his actual artwork for his Spirit until Sephiroth's DLC. Having to go through even more of that just to reference even one other game is clearly not worth that kind of trouble unless it's gonna be going the full mile for a character and stage.
And as much as nobody wants to accept this, if any other Final Fantasy is ever getting into Smash realistically, it's gonna be XIV since that game may as well be all Final Fantasy really is anymore.