You absolutely CANNOT hold the campground at fault for the empty sites. If someone pays for a reservation up front and then cancels at the last minute, and the campground rules permit such cancellation, then everything is above board and legit!
I see a few things have to change ... 1) either the campground has to change their policy of cancellation where there are simply NO refunds. Now wouldn't that bite for those who have legit reasons to cancel!
2) Campers (yes ... you and me) are the real culprits! (and our friends and neighbors and fellow campers) ... WE are the problem! We are basically a selfish people who don't give a moment's thought to anyone else. Remember, this is an extremely selfish- "ME" generation we are living in today!
3) Campgrounds could just do away with a reservation system and make each camp site a camp site a "first come - first serve" campground ... now wouldn't that take care of those how hog the spots!
But the reality is, if we have the reservation system and (rich or poor) have equal opportunity! Make your reservation 11 months in advance and you'll have your campsite too!