In WI State Parks, the definition of "quiet hours" is that the people in the next site should not be able to hear you. Restrictive? Maybe. Nice to camp at? Absolutely! If you don't like it, go to a "party park".
The hard reality is that people are there to have a good time. Having a "good time" means different things to each of us. Regardless of your definition, people need to be respectful of others. I really don't mind a a group of people next to us talking and laughing until late at night. Its when they take it well into the wee hours that it goes beyond being disrespectful of others. And sorry, just because you think your country western music is the greatest thing in the world, others don't agree. Would you like to hear my progressive rock and bebop jazz? Yea, I didn't think so. Headphones are a marvelous invention.
Then there are "party parks". These are ones, public or private, that management allows to get out of hand. I've seen wild parties with 1/4 barrels and 30 bottles of booze on a picnic table, with dozens of people there. I've seen (rather heard) "stereo wars" where 5 or 6 people in the loop put speakers on their car roofs and try to out blast each other. But the management puts up with it. Why, I have no clue.