What seems to be going on in the OPs mind is a severe case of confirmation bias. He has decided that touchscreen is the only way to go and by dismissing the iPad he is free to concentrate his attack on the MBP.
So, ignoring for the moment how people actually use Mac mini, Mac Pro and iMac, the first consideration is the design of the MBP. There is a large touchpad right in front of the user's fingers. If you touch it, in various ways, your touches are translated to things happening on the screen. It's true. I've checked. ****, it's almost like Apple wrote an operating system around it. Next, you might want to grab hold of an iPhone or an iPad and run your fingers over the screen. Feel that? That's right. Glass. Gently touch the screen of your MBP. Plastic. Hmm. Feels to me like that could be easily scratched. Maybe Apple could change that out for a glass screen without adding weight or increasing the size? It would be easy, with only the entire retooling of the product line to consider.
OK. So we now have some advice for Apple on how to provide this missing feature. I guess developers aren't going to like this. Now we have one member of the Mac lineup using touchscreen, while the rest don't. Sorry, guys. You're going to have to write your apps based on two sets of hardware. No cheating and using iOS versions because iOS devices are toys, not computers. A bit of a revolt from the devs here leaves Apple scratching their heads. OK. So the devs won't do it. Well, we will have to go touchscreen for all the Macs.
iMac users. You'll have to redesign your desk. Your screen now needs to be on the front edge so that your fingers can reach it. Mac Mini user? No more running headless. And by the way, you need this particular monitor that costs twice what your Mini did. Mac Pro? One monitor in future, guys. Can't ask devs to write for your weird requirements. Who needs 4 screens, anyway?
You know? I just thought of a simpler idea. Why not just have Apple close the doors and let everyone buy a Dell running Windows 10? That's obviously where the market is. I wonder why Tim Cook didn't think of that?