Updated iPad Pro with Stylus and Kickstand,
connect a keyboard / keyboard cover and mouse/trackpad, able to run full OS X, but also touch optimized iOS Apps.
I expect at some point soon they will deprecate AppKit, move everything into UIKit and use the iPad Pro as the vehicle to drive it i.e. it will only support iOS and Universal apps.
If you want a laptop that's as small and lightweight as the iPad you can get a Macbook Air.
Even if it only gets used one in a while, every laptop (and desktop) should be able to let you scroll and tap buttons and UI elements with your finger in a pinch.
I still mainly use my MacBook Pro, because overall, Windows just doesn't cut it for what I need to do. And I personally don't really need touch that often -- but every single time I do (on the phone, holding a baby, jerking off with right hand, whatever), it is maddening that it doesn't work.
Even if limited to just basic scrolling and tapping, basic touch screen support is still way better than nothing. I think you are right about why Apple doesn't do it yet, but I think Apple is utterly wrong not to do it for that reason.
It's a classic case of making the perfect the enemy of the good.
Truly awesome touch (and stylus!) support would be great; no touch support at all just feels incorrect.
The nay-saying Apple apologists around here just can't wrap their heads around the fact that Apple are masters of bullshitting people into thinking that they know best, even when they leave out obvious features like a second mouse button. I remember back in the 90's, Apple lovers would actually argue that a single mouse button was somehow better because you had to "think about it less". What a crock of fucking shit! :)
Of course it does or else people wouldn't be buying them. Microsoft is doing 4 billion dollars a year in Surface sales.
I've been using Windows on tablets for over a year now and nothing beats it. I get way more control over my tablet with Windows than I do with any of the mobile systems.
Having a different OS for desktops vs. tablets doesn't make much sense. There may be some things you want to do different from a UI perspective, but that should be alterable within the same OS (and, anyway, with touch increasinging available on desktop and laptop displays and people frequently using tablets with, at least, a keyboard if not a mouse, you probably want desktop and tablet OSs to be able to use the same range of UI capabilities, just with different defaults.)