plus at least the self-checkout software that Walmart uses runs in Java, on Windows, on underpowered hardware, yet still has to interface with the old POS system that's running inside of it. I haven't worked at a Walmart in a few years but when I did, the self-checkout UI system would sometimes get out-of-sync with the POS, due to not accounting for all possible edge-case states the POS system can get into. in order to get the UI system out of such a state, a self-checkout employee would need to hope that the system wasn't too stuck so as to be able to log in with employee credentials, then scan a bar code to log in, then enter a UI mode that emulates the keyboard-and-LCD-driven POS system, then press ESC or something to get out of the unaccounted-for edge-case state. and this is all assuming the self-checkout employee has any knowledge whatsoever of the keyboard-and-LCD-driven POS system that's inside the self-checkout machine, which increasingly few employees have, because they've been using these UI wrappers for so long now. but when I first worked as a Walmart cashier in the late 00s/early 10s, nobody really had any trouble working the keyboard-and-LCD-driven POS systems—pretty much every cashier, whether teen or elderly, picked up how to use the POS system fairly easily.

modern self-checkout machines and touchscreen POSes are perfect examples of heaping more layers of abstraction on top of abstraction on top of abstraction on top of a simple underlying system that really didn't need all those abstractions, but they sure look fancier and apparently that's all that matters, productivity be damned.