In a local supermarket, there are some dedicated tills for the service of shoppers using a basket rather than a trolley. People become conditioned that this is the best choice for time-efficient shopping. Perhaps they even come to see the other tills as trolley-only?
Who knows? But there must be some reason why today eight people stood in that line when three of the other tills in their line of sight were totally unencumbered by any shoppers. As Tara says counterintuitiveness is the new black.