I too have been dinged a fee for changing my reservation. One time a wild fire closed the park, not my fault but oh well. My problem is fellow campers are gaming the reservation and cancellation system. All to often I have problems making a reservation because a park is booked full and then I show up at an empty facility. The park is losing revenue and people with families that have to plan a trip in advance can't find spots. Some will reserve their favorite campsite for every weekend of the season then cancel at the last minute and pay the $8 registration fee. $104 for 13 weeks of automatic camp site is a pretty good deal. No consideration at all for their fellow campers.
My solution is for Reserve America is to charge $100 reservation fee for the first campsite reserved. When you show up you get $92 back . Don't show up, lose the $100. The only way to stop the abuse is hit people in the wallet. The RV population is growing fast, the campsite population isn't. Full campgrounds will help alleviate the problem.
Sorry for the rant and I know it strays from a well intentioned OP post but reservation abuse is one of the few things that make my bottom red.