As others have pointed out I think some people just do not like being to isolated. There are times that I have felt like a camper magnet. :R In established campgrounds you have to expect this to a certain extent even if they are almost empty. This Fall we were camped in one of our favorite National Forest Campgrounds that was empty when we arrived but after a few days there were five campers all in sites near us. This Campground had 66 total sites.
To me far enough away is so I do not have to hear their generator or their music.