Without the human and aesthetic nuance needed for fiction, informational content, including much nonfiction, can be very effectively rendered by machine voices, especially if the operation providing them does rigorous testing for mispronunciations, syntax gaffes, and so on. Text to speech can offer a far more affordable route, both in time and money, to getting backlisted titles onto the busy audiobook market.
Source: Germany’s Bookwire Now Offers Artificial Narration for Audiobooks