When you buy a book, you're also buying the right to read it aloud, have it read to you by anyone, read it to your children on long car trips, record yourself reading it and send that to your girlfriend etc. This is the same kind of thing, only without the ability to do the voices properly, and no-one's going to confuse it with an audiobook. And that any authors' societies or publishers who are thinking of spending money on fighting a fundamentally pointless legal case would be much better off taking that money and advertising and promoting what audio books are and what's good about them with it.
Publishers really seem to be out of touch with the way the world is moving. Pretending the world doesn't change and holding onto outdated ideas is not useful.
Related: What is Wrong with Copyright Taking Public Good for Private Special Interests - Innovation and Creative Commons - Recent Reading - Publishers Continue to Fight Open Access to Science