I wondered if that might be the concern. Water suply, drainage, soap in runoff, and splashing other trailers in tight spaces could all be reasons to prohibit washing RVs in campsites. None appear to be issues for at least some campgrounds, including Nk'Mip when I was there
; rules may have changed.
Washing is not mentioned in the currently posted Nk'Mip rules
. In contrast, the place with the RV wash (which has smaller sites) has a rule that says "No hose washing of vehicles in R.V. spaces. Please use R.V. / car wash." My guess is that whatever facility Nk'Mip provides, the trailer can get clean.