There are plenty of countries where iPads are out of reach for regular consumer, and Android Tablets are in practice phones with bigger screens, given how little the ecosystem cares about them, so that leaves Windows devices as only choice for consumers.
Desktop replacement for pen based workflows, like drawing, designing diagrams, architecture sketches, UI mockups,...
When coupled with keyboard, office like workflows, coupled with the pen to do the drawings instead of trying to use the mouse as pencil since many users have done during the last couple of decades.
Programming on the go with environments like Playgrounds, Pythonista, Continuous, Shaderific.
Android keeps having problems because Google is unable to drive the ecosystem to actually care, what a surprise.