For a start iOS does multitask and for many apps automatically scale up to larger screens. Those two points have nothing to do with why people rarely use iPads for productivity (whatever that means). It's because the form factor, input method and brand lends itself to consumption.
It's great that you find W8 to be the best of both worlds. But you are the anomaly right now. And for me personally I like having two devices dedicated to what they do best, "work" and "play". I think Apple may just too.
Well, i'm always reminded of star trek tng, where all devices are touch devices, even the engineering workstations, and it makes perfect sense. For me, it's not a question of whether we're headed for an all-touch future, just a question of when and how. I'm curious what apple will do when they eventually bring touch to the desktop.
It's great that you find W8 to be the best of both worlds. But you are the anomaly right now. And for me personally I like having two devices dedicated to what they do best, "work" and "play". I think Apple may just too.