Is this the explanation? :
"A disclaimer: the National Electrical Code is from the National Fire Protection Association and is not a law. However, almost all community building codes incorporate it into their code. Many amend it in some way. So not every campground - or RV - in the country is wired to the NEC."
Nick Crowhurst, Excella 25 1988, Dodge Ram 2500 Cummins Diesel. England in summer, USA in winter.
"The price of freedom is eternal maintenance."