had my fill of campgrounds

Niner, you are right that the quiet hours are supposed to start at 10. But large groups of drunk young people sometimes don't follow the rules. (Older people who have consumed even minor quantities of alcohol usually fall asleep before 10 -- please don't ask me how I know that.) And it is not a good idea to politely ask the party people to be quiet -- they are surprisingly disobedient. And there is no ranger on duty, and the campground host is already asleep, with earplugs firmly in place.

This scenario has only happened to us twice (both times in the local mountains of Southern California -- imagine that!), but it is not pleasant.