The thing is about grocery stores seems to be: if you're of middling intelligence, you'll almost immediately be bumped up to manager. I knew a guy who was lazy as fuck but was semi-competent and was moved to manager after like two months. Same for my neighbor's daughter, who's smart but she's 20 and this was her second real job. Boom, manager after two months. She hates it now because she has to deal with all the drama of the people who do make close to minimum wage, but she's making decent money for her work experience and can do it while she's in school.
So yes some grocery store workers who stock shelves or put together to-go orders don't make much, but they also seem to be the ones that can't do much.
Worked for an Art shop years ago, amazing the amount of back-breaking work that goes into it from bringing clay to reams of paper upstairs only to have to bring them down again to restock.
Called in sick one day, the manager sent me some bitchy text and claimed the owner had said it.
I stormed into the office the next day and asked them to fire me so I could claim unemployment benefit, the two people in power barely met my eyes. Owner said he won't won't fire me and I said I wanted to be (cash under the table job, no wonder and it was a pittance). Pointed to the manger and told him he needed to get out from under his Mothers skirt. (nearly 40, living at home).
Then later I had a knock on the door, jumped on the window-sill and looked out. The same manager saying he'd quit with a big smile on his face, just told him I was cooking dinner and shut the window. Some people simply never grow up when provided a buffer by the parents, they're completely oblivious to real life.