I think a number of factors play into it:
1. Proximity to an urban area - is it an easy part day drive from "home" to the CG., especially if that urban area is of the type that can support easy storage of an RV when not in use (suburban lots, lots of storage lots, etc.)
2. Is there a strong "outdoor" tradition (camping, hunting, fishing) culture in the region?
3. Are there noted frequent festivals/events in the region?
4. Is the CG itself in the more desirable range of amenities - "family friendly", "resort style", etc.
All of it plays into the RV boom of the last several years - more RV's, with people inclined to use them.
Madison and Milwaukee - huge source of people with RV's who want to get away for a weekend. Philadelphia - not as much, even though it is a big tourist destination!
So easy for a CG to not risk having empty spots vs other areas where they'll hope and pray enough will show up to keep them operating.
