The last NFS CG we were in we were told there is no saving spots. You pay for the site, put the tag on a post and have to occupy it.
Back in the late 80s and 90s we use to meet friends at a county park system that was all first come and all it cost was a $50 yearly vehicle pass. It was common to see a cooler chained to a table for a week. They would camp the weekend and leave their cooler for the next weekend.
It got to the point that all of the prime spots and sometimes half the campground had coolers and the park change the policy to any unattended gear would be removed. Soon after that they started adding electric and charging so it didn't matter.