Typically humans will form a queue if there are multiple registers open. The term first in first out (or FIFO) comes to mind. However, there are people who subscribe to the LIFO life (Last in first out). LIFO is our natural inclination, we are self-centered creatures and have our own interests in mind. So when someone bypasses the established queue, simply give them a reminder they’re not the only person in the store or on the planet.
For instance, I was checking out at a sporting goods store and approached the register. At first, I thought the checkout was empty until I saw the queue of four people waiting for the first available cashier. I took my place in the queue. As my turn approached a person jumped in front of me and began to place their items on the counter. The cashier said nothing. A person behind me said passive aggressively “Some people don’t know where the line starts”. I approached and politely informed the lady that the line started (I pointed in the direction of the 5 people behind me). She said something like “she didn’t see the line”. I replied, “Yeah, it’s right over there”.
A queue makes sense if you are in a busy store that’s understaffed. It’s the faster way to check out. The only problem is the person who starts the queue has to enforce it for the second person who arrives. You have to space yourself at the just the right position between both registers. It helps the register are within close proximity.