I too would be rather disgusted by a mandatory unadvertised amenities fee, and doubly so when said amenities are not operating. Possibly they consider things like roads and washrooms and picnic tables to be amenities, and so logically charge an additional luxury fee when the pool and store and mini golf are in full swing? Otherwise, it seems kind of like a hotel charging all the guests for valet parking, including those who arrive by taxi cab.
"And in a vision Iphigenia saw her brother Orestes, who was being chased by the Amenities; and he cried out in anguish: 'Oh ye gods, who knows what it is to be running? Only he who is running knows."
(From PDQ Bach's cantata masterpiece Iphigenia in Brooklyn)