And since we're being pedantic here, let's talk about definitions. A mobile operating system is one that has been designed primarily for devices intended to be carried on one's person, such as a phone or tablet. A desktop operating system is one that has been designed primarily for devices that are large enough to be stationary during use (e.g., workstations). Both form factors have unique requirements and capabilities, and need vastly different user interfaces.
Further, you seem to be arguing that the kernel (and only the kernel) is what defines an operating system. If that's the case, then Android can only properly be described as a fork of Linux, not Linux itself.
And one of Android's original use models was a non touch screen connected to a keyboard (mainly for Blackberry style smartphones before they were sure that slates would take off, but still...).
Of course I use it mostly to play around and do tests.