@InquisitiveOne: I certainly agree that chapter titling is a useful feature and chapter artwork can enhance the user experience.
I'm not a professor but I have prepared audioBooks for courses of lectures to be distributed to students. You'll find that sort of thing on Audible in the various "The Great Courses" offerings.
Also several years ago on an earlier thread lamenting the loss of chapter information in iPod/Music app on iPad, there was a user who said they were from a federal agency that had developed a training manual that included audioBooks prepared in-house and the loss of chapter information and navigation was particularly irksome in that application.
One of the benefits of the audioBook format (m4b or aa) is that large chunks of material are in a single file / segment and a reasonable player will "remember" the last location within the file; however, schemes based on mp3 / chapter don't work so well since players usually don't long remember the last track heard in an album.
Another benefit of the audioBook format is that bundling multiple chapters together in a single file ensures the play order whereas separate mp3 files can be ordered iin various ways depending on whether file naming or id3 tag naming is used and whether the information is consistent between these.
One of the irksome aspects of the removal of functionality from the iPod/Music app in iOS is that was originally the only way to playback audioBooks from a variety of sources other than the iTunes store (which as far as I know exclusively distributes Audible content).
Since the early days other audio book players for various formats and sources - out-of-copyright readings, public libraries, and so on - have appeared such as the BookMobile and AudioMark and the Overdrive apps.
The Audible app does not provide for any method of loading audioBooks other than via the Audible cloud and the ability to "play" audioBooks from the iTunes shared "MyLibrary" area expressly will not present chapter information to the user - instead a notice is presented saying that the chapter information from the shared library area is not available.