What the system does is the rostering system preferences the workers with the highest scores when assigning shifts. And I suppose makes this number viewable to the workers so they can see why they have to optimise.
You do not need AI to treat the workers that have historically performed well (as measured on some quantitative scale) better than others. Most businesses just don’t do it, as finding an objective scale is hard and people have good reasons for underperforming for periods of time (sick leave, parental leave).
The supply of even untrained workers is finite, so you have to treat them as people.
Ok, let's roll with that. If I'm Alice, why do I care about Bob's score? Why do I care about your system at all? I'm trying to pay rent and not work on my kid's birthday. WHO is going to explain why the frowny faces matter? That person is your middle manager
Sure, and workers have great fun exploiting the hell out of whatever shitty metrics they're given but certain stuff just doesn't get done, and workers who like dealing with humans (probably the best sort of workers to have in a retail organization...) leave.
We could do this with developers too. Give the biggest raise to the developers with the most lines of code committed, and maybe design a shiny dashboard with it as a number to replace the project manager. What could possibly go wrong?