> fetch items in a store. Why?
Because the presence of a human likely prevents shoplifting and / or vandalism. It must make economic sense for the gas station owner to employ a human, and I suppose this is the sense.
What actual useful skill do you think the gas station keeper could learn? Is their employment the thing that prevents them from learning these skills?
> What actual useful skill do you think the gas station keeper could learn?
I mean, it's possible there are useful skills they could learn but there's not the interest or desire to learn those skills. It's completely possible that person is perfectly content doing that work.