> What if I want to listen to an obscure book? Should I be paying a human narrator to narrate my personal library?

You weren't doing that before AI either, were you?

The practical answer has already been "you pipe an ebook through a narrator/speech synthesizer program".

> The copyright holders are incentivized to make money.

Regulations exist. It'd be rather trivial to pass a law mandating every ebook sold to be useable with screen readers. There's already laws for websites, albeit a bit poorly enforced.