In Doug Hajicek's post on the BFRO Facebook page, he said, "They hate getting their photo taken but are not shy about touching our smooth objects!". This is something that they can't get the same experience from water or in the woods. We all love to touch or handle things that are new to us, especially when young.
Totally agree. A few posts in this thread speculated on the glass being intriguing to them. No doubt it is but I would speculate that is not the reason they get close to the windows. To me it looks like intentional mischief. They leave hand prints, rock the camper, smack the windows because they know they can get away with it. They should just use their mindspeak to ask people to leave. Show some manners.