Some people suggest that playing games like Farmville is a waste of time. Well, maybe so, but a lot of things people do are not overly productive, right? Well, what's wrong with listening to a book at the same time?
One thing audiobooks do is provide an alternate version of story the story in print. (Yes, I have read Gust Front twice). For me, beyond entertainment, listening to audiobooks helps me improve pacing and dialogue in my own writing.