Hitchikers Guide was a radio-drama, originally. The book was not just a written version of the original. It's a distinct work, like a film adaptation of a novel.
As you said, audio productions if all kinds are nothing new. That said, audiobooks are still mostly just an audio version of the book. They're not longer or shorter. They don't change the jokes.
David Goggins book , SEAL super tough dude that runs marathons on broken legs, has a narrator with breaks between chapters where narrator interviews him about what they just read or about the next section. Actually worked out pretty well. Thought it was smart.
Peter Attia, internet famous doctor, changed some things in his audiobook and included special things.
I only have 200-250 audiobooks unlike some here and those are the only two where something special is done for the format.
For a brief period I got into listening to classic radio dramas. Surprisingly hard to find. For as much screen time as I get, I do like to be able to just listen. Plus, I think it helps with my concentration.
As you said, audio productions if all kinds are nothing new. That said, audiobooks are still mostly just an audio version of the book. They're not longer or shorter. They don't change the jokes.