This is the same as the jump from iOS 6 to iOS 7, except that was more UI code. It was difficult to support both and keep the correct look and feel between the

This is the same as the jump from iOS 6 to iOS 7, except that was more UI code. It was difficult to support both and keep the correct look and feel between the apps without a lot of extra work, even more if you weren't using auto layout. The basic controls changed a lot and the change with the status bar still affects apps today.