One major thing that more than justifies Theatrhythm Final Fantasy's existence

I've already said I don't think much of the game based on the demo I played but I have to say the concept is a great one.

The reason of course is that the most of these RPGs that anybody ever plays is the music. Someone could say that Final Fantasy VI is the best game ever made and yet, they may not have even completed the game — but they would almost certainly have spent countless hours listening to the soundtrack over and over.

Maybe they even went so far as to play the soundtrack through Vib Ribbon on the PS1! Many would probably do that and now they have a full game available to them that gives them that chance.