Earlier quoted context omitted.
I disagree that it's a small design change. The decision to use finger input as opposed to stylus input has a cascading effect on the whole UI. Fingers are too fat to click on lots of little buttons, so you have to use direct manipulation everywhere you can. Take something simple like zooming or scrolling a page. In Windows Mobile circa 2006, the basic paradigm was the same one you'd use on the Xerox Alto in 1973: cl…
This is a fair point, but that's the engineer's point of view. Looking at it from a product manager's perspective, why did so many decline to make the investment necessary to make touch work for the consumer? I would argue that they simply didn't perceive the enormous difference it would make (ie, that the risk was worth the reward). Faced with the engineering challenges you describe, they decided that there was just…
Your contention earlier was that stylus -> touch was a "tweak." My point is that it's not just a tweak, it's throwing out the existing model and starting from scratch. You implicitly acknowledge that by referencing the investment to make the change, an investment that is incurred by having to throw out the existing design and start over.
Touch was not a tweak. It was throwing out the steering wheel and asking "so now how do you drive the car?"