UEFI is a technology that forces a computer to only load a digitally signed operating system. This has some security benefits, as it makes parts of the operating system unbootable if they become infected, since the viruses won’t be digitally signed by a reputable vendor.
Great idea, right? From a security perspective, absolutely. The more attack vectors for viruses we can eliminate, the better off we’ll be. But Microsoft’s policy on ARM systems shows how it can be abused.
There was some concern that Microsoft would use UEFI to lock anything but Windows out of PCs. As a monopoly, Microsoft can’t afford to do that. Bill Gates was willing to take chances with the Department of Justice; Steve Ballmer has been less so.
But Microsoft takes a lockout stance on ARM-based systems. Microsoft can get away with it there, because Microsoft isn’t a monopoly on ARM. And on phones, we’ve never switched operating systems. We’re used to buying an Android phone if we want Android, an Apple phone if we want IOS (the Apple variety, not Cisco), or a Windows phone if we want Windows.