Back when Microsoft first split Windows 8 in twain, it initially called the two divisions Windows 8 and Windows on ARM (WoA). Windows 8 would be the full-bodied x86 version of the operating system with every bell and whistle, and Windows on ARM would be a cut-down version designed for low-power ARM SoCs.
Most notably, WoA lacked the capability to run any Desktop apps that hadn’t been pre-approved by Microsoft (i.e. Office, Paintbrush, and that’s about it). Outwardly, Microsoft’s justification was that it wanted to ensure a smooth and reliable experience for people with WoA tablets; it didn’t want tablet users to be bogged down by toolbars and malware and other third-party Desktop software. Internally, though, I think that Microsoft was taking the first steps towards killing off the Desktop entirely, on ARM and x86.