We travel with our dogs (under 20 pounds). Looked at a campground website we were considering and they do not allow the open top pens but allow the full enclosure crates. First thought for not allowi...
Some dogs are climbers and can get out of pens you would not think they could. And also people put larger dogs in pens too short for the dog's size with the potential of them jumping out if another dog came in the area. Easier to just enforce a no open top pen rule.