There are a lot of books that don't have (and likely not going to have) audiobook versions. So there is some use for getting better text to speech with the extra stuff an AI could add. And of course have accessibility options that don't have such robotic sounding with bad pronunciation.

That being said, shit is about profits first and the other stuff is not the focus. While I would love to listen to some books with the voice of the authors (or even could be neat to hear voices of podcasters I like read them). I would rather hear hear them read by people that either just really like it as a hobby or wanting to practice voice acting if the authors/podcasters aren't in control of their voice an AI is using. Which reminds me that I should check LibriVox for some non-official audiobooks that I want to read but am too busy to do so.