They spoke to this quite a bit during the BUILD conference. In short, Microsoft is expecting that the days of computers - all computers - having a screen you can't touch are going to come to an end.
We're going to look at non touch-sensitive screens like relics of an old era.
If you buy that future, you may also come to the conclusion that your flagship OS and cash machine had better be ready for it. And, clearly the last few shots at making a windowed UI touch-enabled didn't go so well.
Personally, the only way I would spend any extra on a touch screen for a desktop is if it was built into a drafting table-like surface, so that it could be used ergonomically. An upright touchscreen causes gorilla arm syndrome, and is worse than useless to me; these touchscreen desktops on the market today from HP and others are just way off the mark as far as usability.