Microsoft's long-standing strategy, and recent ad campaigns, tout "one experience for everything" -- Windows Phone, Windows RT for Tablets, and Windows 8.1 for desktops, but despite their similar appearance, all three are distinct systems with their own apps. Your long-beloved Outlook and Office are half-functional on mobile devices.
It's been this way forever. When MS had Windows CE on smartphones, there was the familiar "Start" button and Windows interface, but the apps differed. Today, there is a tile-base interface, and once again, incompatible apps. Different decade, same debacle, in part because of the underlying hardware.
In a few years' time, however, that could change, perhaps because of the chips (which we discussed earlier) and if not, there's always a software-based backup plan.