A visitor even for a short time uses facilities, needs parking, increases liability risk. In my park we insist by law all visitors must register, not necessarily pay, dependent on length of stay and intent wheather to use camp facilities.
Our state requires all persons that visit register so that they can be contacted and counted in the event of a natural or contaminating event. Think terrorism, flood, vandalism or contamination of our drinking water. Overload to washrooms and facilities increased. Where do visitors park? On the site on our grass or in overflow parking. They dont want to park where we designate, they want to park at the paid guests site. Do we have paved or gravel parking for more than 1 vehicles per site? No. Its planned that way to keep traffic and congestion down.
Under federal and state law unauthorized visitors to public or private property is a tresspasser. Unregistered visitors do so at their own risk
When public or private property is held out to the public for fee, even visitors are responsible to comply.