Maybe just to make the lens more useful for other photography? Just another feature to give it more value? I'd imagine the af would keep some traveler from carrying another lens. I've never owned a TS lens, so just spit balling.
Funnily enough, one of the reasons why I love using my T/S-E 24mm is *because* it is slow to use. It takes time to set up a tripod, adjust the tilt and/or shift, and focus manually, during which time I'm spending more time also studying the composition, and noticing/eliminating distracting elements in the scene. If you haven't used one, hire one for a weekend and give it a try, it will be a revelation!
I'm sure there will be someone, somewhere, sometime, who can find a use for AF in a T/S lens...
and yes, It will be very interesting to hear Keith Cooper's opinions on this - if *anyone* will know how to get the best out of it, it will be Keith.