We host at different campgrounds around the country, sometimes we have problems with squatters who try to take reserved sites but they eventually leave. There are sometimes issues with campers due out but enjoying the day, fishing or boating and can't be found creating a problem for everyone.
We also have a reservation loop that allows a FCFS for only one day at a time people try to do multiple days with the payslip envelopes, sometimes it works out other times they have to relocate in the park if there are spots available. It uses a iron ranger and refunds are very difficult to impossible. Know the rules and print them out it seems every campground is different.