Remember back in the day when you'd read about "The Car of the Future" in Popular Mechanics magazine? We dreamed of 3D highways in the skies; of a family jaunt over the Grand Canyon for a look-see; then to Seattle for lunch parked around the rim of the Space Needle. What ever happened to those cars? Where did that dream go?
Well, it turns out it's a lot easier to say, "anti-gravity drive," than it is to actually build one. In fact, it might be enough to observe that bubble roofs make it hard to have a windshield wiper or windows that open. It's just so much easier to dream of the future than to actually pull it off. Doesn't stop us from dreaming, though.