The blame for this rests squarely on Gates himself...
... as he was the one who demanded against all reason that Windows CE had to have all the trappings of its desktop big brother, right down to the Start button, on devices with screens where this made absolutely no sense¹, all in the name of "preserving the Windows franchise". Apple may be overly precious about their user interface but even they realised that the user interface for a phone or tablet has to be different from that for a desktop computer. IIRC, the later versions of Windows Mobile started to fix this lossage but I think the damage has been done by then: Windows on portable devices just never felt right and the continuous chopping and changing made it clear that Microsoft themselves never considered it a priority.
(¹ We'll gloss over how Microsoft then went and did the same thing arse-backwards for Windows 8, demanding against all reason that the desktop UI had to resemble that of a tablet)
Biting the hand that feeds IT
