Many of the quirky rules you'll see at RV Parks & other entertainment or recreation venues are required by the insurance company that provides liability insurance for the park. The helmet rule, no skateboards or scooters, restrictions on dog size or breeds and other rules are mandated by the insurance company otherwise the park would lose their liability insurance.
Libility insurance is expensive and tough to get, so the parks abide by the rules. I have a friend that had one of those small amusment centers in a tourist town...he had a go-kart track, water slide, small roller coaster and other fun activities. His insurance was cancelled due to an accident that was the fault of a patron, not his employees or equipment. He tried to find reasonable insurance from another insurer and ended up having to close the business due to the high cost eventhough the accident was not his fault.