This situation recently happened to me. It occurred because the store in question has an automatic barrier across the entrance. You can only get in that way, not out.
The store has multiple checkout lanes but they're so narrow all it takes is one small woman with a hand bag to block them. Thus, during busy times, like Christmas, all the checkouts backup with queues of people carrying whatever it is they want to buy.
I just want to get out of the store but I can't. I'm a retail hostage, forced to queue because the store is too cheap to hire a door attendant to monitor customers, not making a purchase, as they leave.
I tend to avoid stores like this but sometimes their discounts are just too enticing. Before I know it I'm in the store again, they've sold out of what I came to buy and all the checkouts are clogged with people - half of them just trying to get out.