I don't see who is refusing to sell you a phone with various attachments that make a workable computer (especially given 3rd party providers). I just bought such with an iPad. You could do something along the same lines with an iPhone I suppose but I'd probably find it unsatisfactory. Still on the fence whether the iPad is still a fully satisfactory companion device for traveling in general.

In the Apple ecosystem, the one “refusing to sell you…” is Apple, and not only the required peripherals but also not making the software work that way. Because if they did, then you wouldn’t need to buy a Mac.

Macs are not especially relevant to Apple revenue at this point. iPad plus magnetic keyboard is getting pretty close. Still not sure that better multitasking would push me over the edge to not wanting a MacBook for serious day-to-day multitasking work.

I do think they're trending in that direction but I actually like that they're not pushing people faster than feels comfortable. I expect to see a convergence of iPads and at least MacBook Airs but we're not quite there yet.