If they own the land I don’t see how other people would be affected unless they are violating some other laws which could be enforced separately from the RV question (e.g. trash on property, whatever else you are thinking of).
The main idea is that it negatively impacts their property values, because a home is not a home in a lot of places in the US. A home is the largest financial investment most will make in their lifetime.
There's tons of crazy stuff a neighbor could do to affect property values, why single this out specifically for that reason? A clean RV sitting on property is a lot less bad than building a mountain of tires in your front yard or having 40 dogs (random examples)
I'm not saying I agree with it or don't, I'm saying that's the common reason you'll hear from any of the HOA types, real estate developers / appraisers, etc.
Ah got it, yeah fair enough that is probably the most common reason for it that I've heard too
Or a tent since you might as well not invest a ton into what you're doing as it's illegal.