I prefer to read for myself. I like to imagine characters' voices on my own. I also sometimes have a tendency to space out while reading. With a book, this isn't a problem because I'll still be one the same page. If I was listening to an audio book, trying to find where I was would be a pain.
I have listened to one or two audio books while riding in my brother's car. They were autobiographies, so imagining voices wasn't as big of an issue, and I managed to pay pretty close attention. Still, it's not something I'd do normally (though my brother DID give me one read by Tim Curry, so I might just make an exception, hahaha!).