"Such a simple, obvious idea"
Moving the keyboard on a laptop from the front to the back was far from an obvious idea. To get the maximum screen size on the minimum footprint, the screen needs to be as close to the hinge as possible. If the keyboard is at the back of the case, the user's hands will block his view of the bottom of the screen. Apple got around this by raising the screen, but users paid for it with a slightly smaller display and a significantly thicker device.