Clearly they are restricted to their own property. It’s unambiguously implied. So property ownership is at least somewhat depicted. Maybe they don’t own the side of the tree, but clearly they aren’t allowed on each others. Plus, there’s the whole thing about how analogies work. They all break apart if you stretch them beyond their point. Might as well just ask why equality isn’t just burning the tree down. It’s as nonsensical as your question and just as valuable to discuss.