I was staying at a free campsite years ago which was maintained by the Maine Forest Service, there was a young family in a really nice site nearby. When they left I took a walk down, thinking about using it... The fire pit was full of diapers, while others were tossed into the lake. Yet these people had been swimming there.We used to come to a nearby lake with kids. The shore was littered with cans and bottles. When the IA bottle deposit law became active in 1990 we used to bring plastic bags and kids spent hours looking for cans to return. They earned significant amount of money that year. The shore was more or less clean within single season. It got somewhat worse lately though because many plastic bottles are not refundable.
When I left after 3 weeks I cleaned up, and left a nice little pile of firewood for the next campers. I happened to be going past just 4days later; the site I had been on was strewn with litter, and somebody had taken a $*** in the firepit... despite the fact that there was an outhouse not far away.
Not long after that the MFS stopped maintaining campsites, many people got PO'ed because some became private, pay-to-use, while others were simply closed.