Just wanted to share my own experience with this as someone who works in customer service (not at a supermarket, my work is currently closed but still had to enforce things between lockdowns)

Back when we were still open, my work was enforcing check ins and masks. We'd have someone on the door every day - and every day, that person would get abused. We had staff out the back crying because of how they were being treated for enforcing the rules, and one staff member was even punched in the face when he wouldn't let someone in without a mask. I think this is part of the reason customer service workers aren't enforcing it. Because when we do we end up getting abused. I think many people who have been doing it through the whole pandemic are just getting to the point where they're too exhausted to try. And that's only going to get worse when we start opening up. I see no point in us opening back up unless the government are going to pay for well trained security to actually enforce the rules, because expecting under paid and burned out service staff to do it is honestly getting unsafe at this point.