It's not a huge leap from modelling the game of chess to modelling the skill of chess-playing. Stockfish already offers post-game analysis. Imagine extending that to analyze a players entire career, and offer a series of problems, games against specially-constructed opponents, analysis of relevant historical games etc, all of which are designed to help the player improve. Given Siri, Google Now, Watson and so on, we're probably not far from being able to have a meaningful natural-language conversation with a computer on a narrow subject like chess.
One could imagine this kind of thing being extended to teaching other, similarly focussed skills, at least for beginners. Piano. Tennis. Rock climbing. Maybe even things like soccer and basketball.
But that kind of teaching-based-on-deep-analysis is a long way off for subjects like physics or electrical engineering. Computers can't do physics, much less evaluate human physicists. The best we can do in these areas is something like the Khan Academy, where computers present "content" created by humans, administer standardized tests designed by humans and present the results to humans for interpretation.
So yeah, teaching chess in a really sophisticated way isn't all that useful in the sense that physics or EE are useful. But really, if we could teach computers to understand physics better than people do, we'd use them to make breakthroughs in physics, and that would be a much bigger deal than being able to teach physics more effectively.
On the other hand, we don't play chess or tennis or piano because they're useful, so expert AI teachers for these subjects would be really valuable.