The reason to do this is that just sitting in a chair ploughing through books gets very unappealing after a while. And there’s a lot of books to get through.
I think a lot of people, including, I presume, most who willingly choose to study literature, enjoy reading as an activity unto itself and so don't feel the need to add additional distractions. Not everybody finds sitting down and "ploughing through" (how disdainful a phrase!) a book unappealing.
The reading (listening) of course is not “in the background”. Maybe sometimes you’re distracted and have to skip back 30s and re-listen. Fine. If the game is too distracting, fine, play something simpler, or watch soccer, do chores, anything where the moment to moment continuity does not require effort to track, but still gives you some benefit.