Why does Microsoft make these pointless UI changes? Instead of migrating over existing UI's in the rest of the operating system that use Aero, Windows 10, and e

Why does Microsoft make these pointless UI changes? Instead of migrating over existing UI's in the rest of the operating system that use Aero, Windows 10, and even Windows 98... I know that there are probably different teams for the Shell, and each app but I would hope that there would be a person that drives the overall "vision" of the Operating System.