b) I realize some people dislike it (this I don't really understand but everyone has his/her own preferences and mine are no better than the others).
To perhaps help the understanding aspect:
What should this voice sound like? The way you imagine your character to sound? The way I imagine mine to?
... Like some vaguely urban British woman trying to make a career for herself as a budget price VA for an up and coming game studio?
Should they sound gruff and serious? Should they sound suave and smooth? Should they sound innocent and uncertain? Maybe sinister and cruel?
If a player creates a character, they will usually have some idea of the character they're making in mind - this is the heart and soul of D&D; creating your own character. For most that will include an idea of how they talk, the way they sound, and what their mode of speech might be like... and every character that is created, each different one by one player, and by the multitude of others as well, will have a potentially different answer to that question.
So... IF you create a fully voiced character, that has recording for every dialogue line... that voice is going to sound
*Wrong* for the extreme vast majority of people who create characters to play. Having your character speak in away that is completely wrong for them, that doesn't even remotely match up with how you imagine they might sound, is by far more immersion-breaking and disruptive for players who play characters, than having their character silent in game and their actual manner and mode of speech left in the grey player-filled imagination space.
Now, this doesn't affect players who don't create actual characters - who either just focus on the mechanics of the game, race and class etc., and don't think of their character as a person - the kind of player who names all of their MMO characters BoBTanks, BoBHeals, BoBPews, BoBSneaks etc., and refers to them all as 'toons' (No slight on that - different people have different focuses). It also doesn't affect players who don't ever engage creatively with their character and just adopt a 'take what's given' mentality, and wait for the game to define the character they're playing for them (again, no slight on that - it's just a different way of playing). However, in a D&D-based game, players who create and play characters are the extreme, overwhelming majority group in this sense, because creating your own character is what playing a game like dungeons and dragons is all about.
It would be nice if we had a fully voiced protagonist... IF, and only if, we also, as aprt of that, had at least a dozen or so voice sets to choose from, so that we have a reliably good chance of finding a voice set that is at least passably acceptable for out imaging of our character... and fully voicing every possible voice line literally dozens and dozens of times over is far too ridiculously expensive an endeavour to demand.
This is why, in other game,s voice sets are mainly in control of short phrases and action barks, which create a consistent sense of how the character sounds throughout the game... but leaves the actual selected dialogue lines silent and to the player imagination. It's far more preferable than having to accept and deal with a grossly unfitting voice.