The people that have responded to you seem to be focusing on using touchscreen in a desktop-only/work-only environment, but as an owner of a Surface Book I think that's wrong. When I use my Surface Book for work I very rarely touch the touchscreen because, like @fauigerzigerk said, shoulder pain would become a real problem. Instead, when work is over I detach the keyboard, turn the device into a tablet, and switch myself over to "consumer mode". That's when I use the touchscreen; that's when I break out the pen and start drawing; that's when I switch over to using Windows Store apps because they're built for touchscreen; that's when I switch open Edge because it supports touch gestures; etc.
Of course that would assume Apple builds a device that can detach its keyboard or operate as a 2-in-1 where the screen folds over. I agree that as it's designed right now, a Macbook with a touchscreen would be a bad user experience.
This is just an anecdote, but when my last Windows laptop died in October I looked really hard at buying a Macbook and eventually decided I couldn't live without the touchscreen. Pardon the pun, but being able to touch anything on my screen like I can do on a phone just feels right.
(However, I will say that my default work setup [0] is to flip the screen over, place it on my laptop stand and use it as a second monitor - a decent configuration for annotating documents or taking notes with the pen.)
[0] https://i.imgur.com/sDNYoDF.jpg