Authors might want to use audio as a medium because it is easier. It is easier for audiences to listen to a book than to actually read it themselves. This will help those people who don't like to read very much. They can listen in their car as they drive if they would like to.
This response effectively completes the R.A.C.E strategy by restating the prompt, answering the question, providing evidence (the ease of listening to audio books), and explaining the evidence (how it helps those who don't enjoy reading and can listen while driving).