Aside from what other people here and in other threads said about the player character not acting out in cut scenes, I think I can offer another reason why; animations and different jobs. Whatever fights a cut scene has either uses stock animations or custom animations for the one or two characters that need it. For the player, we can be any job with different weapons and powers, which might require the same scene being animated several times with different animations. Just look at the fight between Raubahn and the backstabber. They both use swords and their animations for the fight go well since their weapons compliment each other and the two characters have similar body builds. Now imagine if we got to fight that snake ourselves in a cut scene with a staff, knives, bows, etc. How would the fight look? Would there be major clipping with custom animations based on the gear we have? How does the player's race/size affect the fluidity of the combat in the scene?