>>994538 (OP)
My guess: less interest. There is software people rely on for work and there is games. macOS has fewer of both, so there is not much incentive for running Mac software on GNU/Linux.
>>994543
Right, people just stick to whatever comes with the PC they buy and don't question it. I switched to GNU/Linux from Mac, to which I switched from Linux, but I am far away from the average user.
>>994555
To the end user it doesn't really matter when neither is native. Adobe software sticks out like a sort thumb on macOS. Pixelmator is much more "Mac-like" than Photoshop. (at least it used to be, I just looked up their site and they have adopted the new faggy design of only one window with baked-in panels).
>>994561
> and more like people just haven't gotten around to re-implementing Apple's native libs
Well, there is GNUStep, which is exactly that: a re-implementation of the Cocoa API. I have no idea how complete it is, but it's certainly old.
http://gnustep.org/