The discs that hold the audio book take up more space and are significantly more expensive than the paper that would have held the same amount of information in text. Audio book publishers shorten books so that they are able to sell the books for less or improve profit margins. People are more likely to buy audio books if they are less expensive, so selling individual books for less may still generate more profit.
When reading, people may skip directly to the information or passages they find most interesting. Since this is much more difficult for those listening to audio books, publishers sometimes attempt to compress the information as much as possible. Time reports that consumers may also be more interested in purchasing shorter books because they involve less of a time commitment.
Some readers prefer to listen to books purely for enjoyment. In an article for The Guardian, one editor describes the way she works to "find the plot" and keep the story moving. This keeps readers from feeling burdened by slower parts of the book, though some of the book's original meaning may be lost.