Re: "It’s a mystery why Microsoft..."
I think there are several explanations, all converging:
a) Ballmer's "take over the world" approach, wanted something unique and patentable that could be used to squeeze out competition forever
b) Sinofsky's "new, shiny" approach to the GUI created the tile screen, because he failed to see EXISTING INSTALL BASE as "important". _EVERYBODY_ was on a slab or phone now, right?
c) The marketing guy who was canned early last year [forget his name] was a big part of this. His market research was *WAY* too narrow in scope, basically interviewing shills and fanbois to get feedback, and ignoring "the rest of us". Keep in mind THAT guy was around for several F-ups, including Vista, "The Ribbon", Silverlight, Win "APE", _AND_ Win-10-nic.
d) Senior development staff "now retired" - and ONLY! ARROGANT! MILLENIAL! CHILDREN! seem to be running the asylum... (it's THEIR TURN to do it THEIR WAY, now, and those old guys just DID NOT KNOW WHAT THEY WERE DOING, so NOW it will be done *PROPERLY* by YOUNG people!!! W00T LOL text-text-text 4" rules)
e) FIRING of the testing groups, so that end-users become "the new testers" for Enterprise. Not even PRO users escape, THIS time!!!
yeah, all of that ARROGANCE and WRONG THINKING had to come from SOMEWHERE, and it happened right there in Redmond, with a capital T and that rhymes with 'C' and that stands for CRAP (which is what Micro-shaft has been EXCRETING these past few years)