It's Steve Jobs' ploy to kill the laptop market. He didn't need the laptop market, he had the iPhone, he knew of the iPad when he demo'd the Macbook Air. Today the entire Mac revenue https://www.statista.com/statistics/382260/segments-share-re... is below 10%.
See, he have started the thin craze and everyone copied. But noone needs a thin laptop. There's no advantage to it whatsoever. People do need lightweight laptops and well before the Macbook Air we had shockingly lightweight ones, my Panasonic CF-Y5 was 1.5kg including a DVD ROM more than ten years ago. It had a protrusion on the lid to create a cushion which made a review to call "the exterior design of the machine's casing is reminiscent of a Sherman tank cross-bred with a 1970s sports saloon". It made it 45mm thick at the thickest point. Still, it was 1.5kg and undestructible.
So, instead of focusing on materials science and building lightweight laptops in whatever thickness a good cooling system would require everyone is falling over themselves to produce a thin laptop. Which, of course, can't be properly cooled. It's just physics. In this case, the Macbook "Pro" is 0.61" high where the Lenovo P52 (which is Pro for real) is 0.96”. This thinness craze killed off the convenient bottom dock ports from the business laptops creating these awkward side docks.
Fantastic trick, Mr Jobs, well played.