Except they cant do that because it means you lose personalization with dialogue - if you notice that the scenes that are voiced the player's character is never acknowledged by name, simply with non personal titles like "you", "the adventurer", "the Warrior of Light", the "Champion" etc, so the player would be restricted to be entirely identified as such throughout the entire game by npcs who are supposedly close to them (this is why also modern FF games do not have the ability that older FF games had where you could name the player's party whatever you liked - it was the price that was paid for having voiced cutscenes).

And given most of the voiced dialogue is often in the "so bad it's good" category, I prefer the approach they're currently taking and do not really wish for them to change. It's one of those situations where you can't have your cake and eat it too.