macOS Isn't as Small As You Think
I think Apple should add touch to Macs, and I think that this will allow them to not only make current form factors better, but it will allow them to create Macs that are more flexible, more powerful, and more accessible than any Macs before them.
That said, there are people in the Mac community who disagree with me here, and their number one concern is that macOS has a UI that is simply unusable with touch. It's the ace-in-the-hole argument, and it's honestly something I haven't pushed back on because it feels true.
My MacBook is a pretty average Mac laptop size, and the iPad mini is the literal smallest iPad Apple makes. Nobody is out there saying that the iPad mini is unusable via touch, in fact many people in the enthusiast community will tell you the iPad mini is the epitome of the iPad lineup.
Given that, I think the touch targets on the iPad mini are reasonable for most people, and I think even "don't bring touch to my Mac" people would agree here.
