One of Microsoft‘s main goals for Windows 8 was to create a market for tablets running its operating system. Windows 8.1 will continue this plan with some new features designed specifically for tablets, including support for screens in portrait mode.
And coming with 8.1, building on our support for small tablets, we’re really committed to completing the scenario, including full portrait support.
Windows was created to run on desktops and later laptops, devices that have no need of anything but landscape support. However, iPad and Android tablet users are accustomed to switching their devices between landscape and portrait all the time. This change will help Microsoft compete better against these rivals.