A cabin is the hardest thing to get in most park systems: there are only ever a handful per campground, they book the day the window opens, and they stay booked through the whole season. When one comes back it is usually a cancellation, and it is usually gone within the hour.
We track live availability at 1,142 campgrounds with cabins across 34 states, on Recreation.gov and 13 state park systems. Every one is rechecked every 15 seconds, around the clock, so when a booked site frees up you hear about it in seconds rather than finding out weeks later that it was open for an hour.