Except when we arrived the people in the campervan were nowhere to be seen (out walking with the dog) and the outfit that left late was , how can I put it, completely established with large awning and having done nothing to start the packing up process. We had no idea who should have left.
As it happens we use this CL a lot (close to family) and it's exactly our sort of site. The elderly owners are lovely people who will often go for a walk around the field and stop for a chat. People who use it are, in many cases, regulars. You pitch where you like except only hard standings used in winter of course.
Although arguably I could have done as you suggest it would have been churlish of me to put the owners into the position where they would be expected to "police" the site.
The truth is that the place is relaxed and anything but formal. (Our kind of site) And the owners simply rely on visitors to "play the game". Sadly, as in many areas of modern life, some people either don't care about disrupting others or are simply unaware of the disruption they cause.
Who can say which "camp" (sorry!!!) the late leavers belong to. A sunny day, a short tow home, why not stay late!