The laptop you're using today, imitates the Grid Systems' Grid Compass 1101 laptop. From April, 1982, the first clamshell laptop was created.
TIME dove deep inside the clamshell design's history. It's easy to see why we use William Moggridge's clamshell laptop design today, because, well, everything else that was proposed sucked. And some computers look like sewing machines or giant calculators. The best bet was the clamshell design. TIME says:
Moggridge's design made for a far more portable computer than the Osborne [the sewing machine computer]. It let the user angle the screen to his or her preference. The backside of the display protected both the screen and the keyboard when the machine wasn't in use. And unlike numerous mobile-computer cases to come, it was mechanically simple. It's one of the most clever pieces of engineering in computing history.