Pure marketing ploy, same as with phones, which nobody wanted thinner versions of ever since we got thin-enough smartphones.

It's hard to market an intangible quality like "increased battery life", but a thinner laptop has an immediate visual, futuristic, visceral appeal.

The new MacBook Pro looks sleek, and immediately makes the 2015 model — once the slickest laptop around — look dumpy and old hat.

On the other hand, there is such a thing as a laptop that is too thick and heavy, obviously. Many PC models still are.