Microsoft gave up on Windows RT to go back to the drawing board and build Windows on ARM. It's the same with phones: they gave up on Windows Phone so that they

Microsoft gave up on Windows RT to go back to the drawing board and build Windows on ARM. It's the same with phones: they gave up on Windows Phone so that they can have a "Surface Phone" do-over in the future. This allows them to introduce hot "new" products rather than updated versions of failed products. There are many examples of Microsoft doing this.