I definitely see cash register/POS systems like this out in the wild, replete with ugly fonts, Windows 3.x style buttons, and even F-key legends at the bottom. So somebody somewhere is thinking of the poor cashiers.

The entire GUI was sold on it being easy to use for beginners. There's a reason why keybindings are today called "shortcuts": Steve Jobs's diktat was that the primary means of giving commands to the Mac was the mouse. Anything you can do on a Mac (except for entering text) was to be done with, and designed around, the mouse. Keyboard "shortcuts", so called as a quicker way to issue (some, but not all) menu commands, were a sop to power users but really were an addition, not essential to use of the program.

Windows, by contrast, was designed to be keyboard-accessible. Not all PCs in 1985 had mice...

I still work on a system where it sometimes says to press F17 to do something…

And no, we don’t have the glorious keyboards from that time :( just standard 104s

I once booted Windows 2003, it is crazy how you can intuitively interact with it via keyboard, without being familiar with that UI or ever having used a computer from even that era. It takes like ~40seconds to figure it out after trial and error.