It's generally referred to a the "commons." If everything was privately owned, we would have nowhere to enjoy nature or other areas of beauty and interest without someone else's permission. Government owned land affords us the permission to be a part of the land. There are other conservancies which also provide public access, but Uncle Sam is the largest of these. My beef is that we're taxed so heavily and still have to pay a fee to enter parks. The Grand Canyon is going to $100 admission fee if I remember correctly.