I don't think people give this enough credit. It's one thing to be shit on by your employer, but having the customers treating like shit as well is just as bad. Getting the double whammy of getting it from both sides must be brutal.
Spent a few years in retail, and can tell you: if management treats employees badly, customers will treat employees badly, which in turn causes another cycle of management treating employees badly. It's a cycle that is caused when management and employees aren't focused on the one thing that really matters in a retail exchange: having happy customers.
I think the fact that Costco employees don’t have to wear a full uniform is part of it. They have a clear identification that they’re an employee, as is necessary, but they also don’t have to wear a uniform that strips them of as much individuality as possible.
At an Amazon warehouse, they go through employees like a runny nose goes through tissues.