There are reasons to make it private, but it's quite different from, say, a sculpture. Clay is nearly worthless, so if an artist turns it into a valuable sculpture, that value was created. Obviously, there's a spectrum here. Even land typically requires an investment to make it useful for anything.
Food is largely created; especially something like sausages or cheese. So the tale of the miner above doesn't really apply. It may not even apply well in that case, if the pheasants were feeding on crops cultivated by the landowner.
