I am not forbidding anyone from having hobbies (though Apple probably is) - but whatever you build will be undone in a year or so - Apple will never permit it.
However, writing a series of mac-like apps for a FreeBSD/Linux desktop, or even a new desktop environment which closely follows Mac, will continue to be relevant work.
The only reason I do that is because I _have_ to do that due to MDM and the fact that Asahi doesn't do the Standby. Excellent hardware, bound by a sad OS.
Why take normal hardware and add a sad OS without being forced to do so?
I suppose "for the sake of it" is a good answer here. For the fun of making computers do something they really do not want to do.
If that's a real example and you didn't make it up, I want to know what pregnancy-test devices have enough buttons to make it possible to control the game. Or are they coming with touchscreens now? Refrigerators, sure, I can easily see that. But pregnancy-test devices? Why would they have enough buttons to be able to simulate WASD and a fire button? The only pregnancy-test devices I've seen are the home test ones where you put the sample in the device then wait to see if there's one line or two (some of them arrange the two lines in a + shape so that - means a negative result and + means a positive result, which is clever), with no electronics. What pregnancy-test devices are using more than that?
An example could be as simple as somebody whose Mac broke and needs to use MacOS specific software and workflows, but can't afford to get a new Mac.
For others it was just about the money. If you needed to run Mac software e.g. Xcode but didn't want to have to buy a Mac for that reason alone it was much cheaper to do a bit of tinkering to get OSX working on the hardware they already had.
When I first build my Hackintosh it took less effort than installing Linux on some of the other computers I had.
I built two Hackintoshes in those years, and they were rock solid. You did have to pay attention to the hardware you were buying (mostly motherboard and GPU), but if you got that right, they worked really well.
Maybe it helps that in my part of the globe Apple was largely irrelevant until they manage to survive bankruptcy with the iPod, and iMacs.
I got my current job thanks to having one. I probably wouldn't have a tech career without hackintoshes being a thing.
So in such case I would have opted out for a cheap PC built of parts running some Linux distro, or Windows, which has most audio and design tooling as OS X has.