Had one instance that we were unabe to make it to the campground to keep our reservation. They had a no refund policy that I was fully aware of so they issued a credit for future use. I was happy with that and used it on our return trip only a few weeks later.
When on the road and need an overnight we call ahead for availability. Some ask for a deposit which I decline and say I will take my chances that we arrive before you are full. Never been shut out...but then we like to be off the road by 5pm. Around 7pm I see a rush of people coming into the park where ever we stay.
Early in our beginning camping days I made reservations with deposit that I lost because of one reason or another not being able to make it to the CG. I learned. I will not make reservations unless it is a destination we are staying at for a week or more. Then I know the rules and their policy and if something goes wrong I talk with the owner nicely and usually come to a happy agreement on future use or if I miss the first night I eat the loss. That's the way it goes.