Reading all these posts got me to thinking. Since the campground was willing to change dates so the OP would not loose his money, I think changing dates would have been the smart thing to do. THEN if he could not make the second dates, rather than cancelling (which, more than likely he would have lost money anyway), just don't show up. Either way, you loose money, but at least by rescheduling you MIGHT be able to make those dates and still have a great time.
Why do an official "cancel", they keep your money, then they book your original site to someone else. Now they have your money, AND the second camper's money for the same site on the same dates. OK, so you'd be making your spot available for someone else. But if customers know they are going to loose money because of the refund policy, it makes no difference to the customer if the campsite is still reserved or not. If the campgrounds realize they cannot book the site, simply because you are a no-show, they might get the idea their cancellation policy is not working. If your spot is still reserved to you, they can't book it for someone else. What would happen if you booked 7 days, but something happened and you couldn't show up until the 3rd day? I've seen people do this many times. So if you are a no-show, the campground would run a real risk if they decided to give that same spot to someone else, and than your day 3, you showed up!
If you KNOW you are loosing all your money, (you may disagree with me here), but I'll do the "no show" instead, just so they could NOT get double money for the same campsite.
I did do this once, (in an Indiana State Park), where the day we were suppose to arrive, something happened and we had to cancel the entire trip. I knew we could not get our money back, so I was just no-show.