I understand why stores have multiple checkout aisles. What I do not understand is why there isn’t a master queue that then allows people to check out in a first in first out manner. I went to Dicks Sporting Goods and got in a line. I then watched other people who hadn’t even been in line before me get checked out as the person in front of me took a really long time to get checked out. If the employees would have said something like “sir, you’ve been waiting a long time why don’t you come over here next” everyone in line would have understood, but they didn’t.
So my suggestion would be the one line that splits off to multiple registers. Seems pretty simple and will lead to less frustration among customers.