Doug,
Agree automobile and RV service are different, but perhaps not as different as one might expect.
Look at the number of after-market service agreements available on automobiles(many call them extended warranties, but they are not). Just as with RV's most require prior approval. I do not know the time difference between prior approval on RV vs automobile. And, particularly on used cars, parts are NOT in stock for the perfusion of makes and models sold-- meaning similar order processes.
I am quite certain there are some well-run RV service/parts departments as well as poorly run ones. Same goes for the automobile business (and most other businesses for that matter).