It's funny you say it that way, because with Windows 8's Start Screen default on all computers, Microsoft was effectively telling keyboard and mouse PC users that they were using the wrong human interface devices, and should have been using a touchscreen (perhaps a Microsoft Surface, hmmm?).
Since the run up to Windows 8, Microsoft's marketing plan for their OSes, and by extension, Visual Studio and XBox. This isn't by accident: you can tell the direction from the comments of Julie Larson-Green (creator of the Ribbon) at the 2013 Wired Business Conference: http://winsupersite.com/window...
"There have been discussions... meaningful discussion [of bringing back the classic Start menu]. But we believe fully in the Start screen and the model of having these live tiles. The [old] Start menu was never really built for multiple applications... the Start screen offers dramatic improvement. Windows today is so much more than launching applications... the [old] Start menu is not the be-all, end-all. [But] the button might be helpful to have on the screen. We're principled in the direction we're heading, but we're not going to be stubborn... It's not to spite you." [Laughs]
Yes, Hanlon's Razor applies here, but it feels like there's been a veritable conspiracy of intentionally orchestrated ignorance in Microsoft's UI design. There was plenty of resistance to the Ribbon when it was forced onto Office, but at least the legacy key combinations remained. But many of those UI changes, as well as the Metro marketing push, were force-fed onto the userbase, so I don't blame those users for complaining vehemently. We're at the point where UI duct-tape utilities like Classic Shell are compulsory for proper usability in content-creation scenarios for an operating system, and right now it looks like this is going to continue for Windows 10, as far as icons are concerned.