BEcause it's a well known fact for years now that blank slate characters and voice acting don't mix.
In theory they do, just in practice it's impossible. I'm sure that even you would enjoy voice acted character more if you had an option of voice with the right personality for every character you came up with, and voice acting would not reduce the number of available dialogue options.
That would just be a 500+gb game with insane development costs.
I think that our main disagreement here with people that like voiced PC is that we like to play unconventional characters while they like to play "Tav" so it's much easier to satisfy them with a voice.
I'm not sure I agree. I have a very active imagination, personally, and love characterization, so unconventional characters come naturally to me. While my character may be named Tav, she's still unique in various ways within my head, and voice acting will not change that. I just fill in the blanks, create explanations for why she would do or say x. It's something I've done with all games with a protagonist, voiced or otherwise, and it's not particularly hard to do without straying at all from my character, with rare exceptions where the only options are those that my character would never
consider doing, which happens just as often with "silent" protagonists as it does with voiced ones in my personal experience. Usually the biggest stretch I have to go with is "It's the right thing to do," or "it's for the greater good," but most of the time it just flows naturally for me as the options make sense with the character, though this may just be because I have a strong streak of making chaotic good characters unless I need a villain (and I don't like playing as the villain, personally, outside of villain protagonist games like War For The Overworld).
(As a side note, I think voice acting only limits character statements somewhat compared to text based, which still has the constraints of only allowing what the devs come up with for the character, meaning you can still end up with situations where your character has only choices s/he would never do the way you imagined them, voicing just tends to reduce the number of options available). Again, all personal opinion.
Also, text based on both sides (to go to the opposite extreme, not to argue against anyone at all, I just feel like ranting a bit about dialogue I don't like) tends to end up with rather wooden sounding dialogue that goes on and on, which is why I write with a text-to-speech program going, to catch the wooden, awkward phrasings that look fine on paper.
The whole voice not matching the character thing (ie a black man with a white man's voice) that was mentioned either here or elsewhere is a valid criticism, however.