At some point when you're developing a Windows 8 App you probably realized that if the app is run on a tablet form factor device you'd want to freeze the app orientation in either landscape or portrait display modes like you'd do in a Windows Phone app. So what you do in Visual Studio 2012 is that you double click on the Package.appxmanifest file so you can start tweaking the manifest settings for your app, in particular is the Supported rotations section.

Since you want your app to only support landscape mode, you check both landscape modes. Then you decide to test if this works, so you fire up the simulator, and rotate it, but instead of being locked in landscape, your app still rotates to potrait mode.

This doesn't work because the simulator doesn't accurately simulate the hardware rotation, as mentioned in the documentation (look under the change device orientation section)

Since that doesn't work, you try to manually rotate your screen using Windows Mobility Center (Windows + X, then select Windows Mobility Center)

And STILL your app doesn't stick to landscape orientation!

So what exactly is wrong?

The problem here is that the rotation preference setting of the app is only enforced on a Windows 8 system with a supported HARDWARE ACCELEROMETER.

Which means unless Windows knows how the system is orientated through the means of a supported sensor, it'll never attempt to switch to the app's preferred orientation.

So you shouldn't need to worry that your preferred orientation setting isn't working, it'll work on any hardware that is properly designed for Windows 8. How do you deal with people who manually rotate their screens using Windows Mobility Center then? Well... did you know you could rotate your screen using Windows Mobility Center? Did you even know that there was a Windows Mobility Center? It should be safe to assume that if someone knew enough to manually rotate their screen display, they'll know enough that not all apps run fine in both portrait and landscape orientations.