I think it's a great idea. There were many times when we just needed a place to sleep, other times when we'd be exploring an area but would spend time at the cg and a few times when we just wanted to go and plunk. For those complaining about cost, just vote with your feet. I've been at private campgrounds whose cost far exceeds any KOA I've stayed at. BUT if it's where you want to be, when you want to be there, with the amenities you want (or not) then it's not expensive. You can't put a cost on memories.
We use a similar system now for hotels/cabins/condos since we don't currently have an RV. Two years ago we stayed at Custer State Park and rented a cabin. In Denmark it was a pricey hotel but the location unbeatable. In Iceland it was an apartment hotel so we'd have room to spread out and the ability to save money on meals, plus the cost couldn't be beat. Last week in St. John (USVI) we rented a condo for the same reason. Although the amenities at the Westin Hotel there would have been fantastic, the price for the rooms or condo we would have needed just couldn't be justified.