I guess the simple answer would be no one has sufficient motivation. Questions like: What's the point? Novelty wouldn't be enough, considering the costs involved. Corporations and banks would be thinking, "Is this a good investment? Will we get a return on it worth the outlay? You see, we don't appear to have any "living god and absolute rulers" to force us into doing such a thing and so...It is likely not to be undertaken. Maybe a country like China could do it. But would they be able to sell it overseas...?