Yes, but at the time that Audible got started, they weren't able to negotiate for these rights. And some companies only re-recorded the unabridged versions after the original abridged versions came out, once the market started to take off. See this Audible Cranks Up
post from the recent Has audible.com quality dropped?
thread for a history of Audible. And see the Publisher's Weekly link that I added to my edited P.S. for a history of audiobooks. Unabridged books for reading first got started in the late 1970s. Audiobooks have really only taken off recently.
The other historical factor you're seeing is the bandwidth limitation at the time that Audible got started. This showed up in both a larger number of abridged audiobooks (which was also more typically representative of the earlier audiobook market) and more highly compressed formats (lower quality but smaller size for dial-up modem transfer and also to match device capacities). The books you cite (like the Grisham books) date from the pre-iTunes, pre-iPod Audible era of acquisitions.