Here's a pointed quote from the article (written by an author who was considering options for the creation of an audiobook version of one of her works):
"The voices of the performers the audiobook company asked me to choose from sounded, if not robotic exactly, more like the Hertz NeverLost lady than Meryl Streep."This quote hits it on the head: Somebody who can provide the voiceover for a 30-second blurb to sell Big Gulps at Seven-Eleven does not necessarily have any idea how to narrate and produce a long-form narrative work in audiobook format. (An athlete gifted in the 100-meter dash would not necessarily be able to credibly compete in a marathon without properly training for it.)
I am NOT saying that a "voiceover artist" could not do a good job with audiobook narration, but experience with one does not automatically transfer to the other.
BTW, another standard conflation is this: the powers-that-be also seem to think that anyone with a Screen Actors Guild membership card can automatically narrate audiobooks. Some no doubt can, but one does not automatically give the other.
Edit Sept. 7, 2013: It appears the folks at Brilliance Audio (who have obviously been in the audiobook business a LONG time) agree with drawing a clear distinction between "audiobook narration" and "voiceover". On their "Careers at Brilliance Audio" webpage, they give this succinct instruction to those who would send them audiobook narration audition materials:
We are not interested whatsoever in voice over or commercial work examples.I'm supposing theirs to be the voice of experience, to which I defer.