People want desktops to run desktop software. Not WinRT/universal/modern/UWP. They did not understand this. So for multiple iterations, they shipped tablets, phones, etc., under the "Windows" brand that could not do what people think of when they hear "Windows".
They should have shipped a device circa 2012 that let you recompile desktop Windows apps for arm. They had the technology.
we are still in the mainframe/timeshare stage.
The PC revolution happened because of very open hardware specifications and a non-monopoly on the firmware (the IBM BIOS was reverse-engineered by Compaq).
There are plenty of reasons for that, chief among them being the staggeringly-uphill battle of Windows regaining any significant marketshare in the mobile space and (presumably) the lack of software compatible with Windows on ARM.
Meanwhile, Android (and Samsung's phones in particular) are quite popular, and the vast majority (to my knowledge) of Linux desktop programs work on ARM just as well as they do on x86(-64).
Snapdragon's 835 changed that. So will the A12X from Apple.
But it's likely a greater chance to see a snapdragon head into a convertible desktop format than an iPhone or iPad, neither even allow a mouse. Still have hope for an A12X powering a MacBook tho.
I bought a Sentio Superbook, and my pixel is the only non-apple device I have so I can try to use it in this manner.
Remember, Microsoft tried this with Continuum for Windows 8/10 and Windows Mobile, it failed. No-one actually wanted the core of their desktop inside their phones. People have partitioned off different use-cases for their PC and smartphones, and the overlap is smaller than designers think.