Multiple OS installs / multiple boxes on the same keyboard.

Then it's "do it 4 times in software for free" and the software is not the same and this solution suddenly becomes attractive.

You could solve it by getting a keyboard that supports macros on the keyboard hardware maybe. Or keep your existing keyboard you know and love and insert this little solution.

I use a keyboard with qmk which is quite similar to this, before that I used a bunch of autohotkey scripts. To me qmk is a better solution since it works on any computer and any programs (autohotkey struggles with some applications that I belive use lower level input handling, I cannot speak for Karabiner since I don't use it), without needing to install anything. To me is a big plus