I suspect this may be one of those places where the code has not quite kept pace with changing realities. With the tremendous growth in the RV industry, more and more people are parking them at their residence and want to have power to them. I know of several who use the RV as a spare bedroom / guesthouse for visitors. Things like water and sewer connections will need to be addressed in their respecrive codes as well.
For my personal RV, I did not install a disconnect switch at the outlet but the breaker is within about 25 feet. I did choose to use a GFI breaker based on how much junk wiring I've seen in RVs. After all this discussion, I think I would use an outlet with an integral disconnect in and future installs I do. If I were to author a piece of code, I would mandate the GFI.
