Let's think this through, if all the campground sites are reserved/paid for then the campground should not book anyone else or should they intentionally overbook, like the airlines, assuming there will be some % of "no shows"?
Why wouldn't the campground contact the reservation holder after 24 hours of "no show" to see if they could re-reserve the campsite?
If the campsite is paid for by a "no show" and then re-reserved to another camper, does the original reservee get their money back or does the campground keep the profit for the double booked campsite?
Seems like a slippery slope to me.