There are several reasons I personally have long been against fully voiced protagonists in crpgs. One is that it can end up limiting roleplay options. If devs have to fully voice everything, that means severely limiting the number of dialoguue options we can have. If the devs see a point where it would make sense to add a reaction, then what would be typing in a line of dialogue then becomes getting a voice actor in, paying them, paying for whatever equipment is necessary to actually record, then paying for the process of mixing and adding the line to the actual game. So by necessity the number of options given have to be pared down just so they aren't prohibitively expensive (I personally am against full voicing even for companions for this same reason. I think companions and NPCs should have occasional voiced dialogue in big, important moments but leave it as text otherwise.
The next reason is actually a counterpoint to what you say about connection. I find that if my protagonist is voiced, it takes away connection. I can't imagine a voice for them, can't imagine how they might phrase things, suddenly they aren't my character, they're the character the developer envisioned. Because devs can't account for every nuance of a character, nor should they have to or even try to. A mute protagonist lets me dictate as much of my character as possible. Frankly I already find BG3 frustratingly limiting in the types of character personalities I can give to my characters, full voicing would only limit me further.
