The opportunity to re-read is really valuable, too. I don't know if my thoughts are more likely to drift when I'm listening rather than reading, but it's absolutely easier to recover from a little mind-drift when you're reading. Pop back and re-read a sentence or a paragraph and you're back on track. Much more complicated with audio. I wonder if there's research done on that? On how steady our tracking is when we're reading... do we generally go in as straight and steady a line as audiobook readers do?
If it weren't for audiobooks, I doubt I'd get much "reading" done. I am a shift-working father of three small humans in a continually-on-the-brink marriage; time for writing, reading, or coherent thought is limited. Without my audiobooks in the car, I would never have experienced Dune or Starship Titanic. Even books that I have read (many times) like A Canticle for Leibowitz and the Gormenghast trilogy were great on audiobook, as the narrator was able to provide a kind of new interpretation on some passages, from the way I had read them myself.