I believe they stated the reason there was no FFXV cross-over event was because they wanted players to get to know the characters and the game of FFXV first, otherwise, the crossover wouldn't really have the same kind of impact. Rather than players going, 'Cool, its <name> I love that guy/girl,' they're left more with, 'Hrmn... generic anime protagonist #14351346543 has a nice outfit.'