CPU architecture I assume is the reason these things cannot run OSX.
That's its main allure.
If one just wants a computer to run arbitrary OS with desktop-like experience there are tons of them, it doesn't even have to be a tablet.
The problem is that you cannot just put a keyboard/mouse centric on a touch device. The entire UX will crumble down. Same story the other way around.
Small things like buttons and textfields need to be bigger and more spaced out. Entire panels need to be redesigned as the control density is lower. To get the same quality of UX you need to design for both interface methods.
iOS suffers the same when attaching a keyboard to an iPad. A lot of small things like workflow shortcuts and navigating the control space with just a keyboard just don't work (yet). Forcing you in either a touch-only mode or having to switch between keyboard and touch constantly.
Not, the fact that it's taboo to control every single app binary and extract 30% tax on everything on macOS is what's making Apple not port OS X.