Especially when there are times in pve you are in the middle of a combo that splits, but a mechanic happens making you need to change which finisher you are using. Such as melee aoe happening forcing a PLD to go out and suddenly that Royal Authority needs to be a Goring Blade otherwise the DoT falls off. With them reduced to separate 1 button combos you can't really do that, unless they code both buttons to go through the motions each time one is hit.