A national park is a vibrant ecosystem that can be accessed by potentially millions of people, all of whom might have some thing they want to leave behind. The

A national park is a vibrant ecosystem that can be accessed by potentially millions of people, all of whom might have some thing they want to leave behind. The Moon is a lifeless, airless rock which is only accessible to a tiny number of people and only in a limited sense. The concerns for preservation are just so different between the two. As far as we know national parks are unique in the Solar system, maybe beyond. As far as we know lifeless, airless rocks are downright common, the only real thing going for the moon is that it's relatively close by.