It’s ymmv. I agree that one single line which leads to a group of cashiers / atm / etc is best. Not every business agrees. Recently at Sf Costco food court, the punters made a single queue for 2 pickup stations. A staffer appeared and directed us to form 2 lines. I was thankfully near the front when this happened so I just got behind one pickup station. After I fetched my order, I noticed that the staffer was gone and there was again a single line of punters.
I think I switched to SCO because of multiple lines at shops. Most SCO are single lines to a station of 2-8 sco POS. I’ll never miss standing in line for a cashier behind a complicated transaction. Ditto for tsa (most usa tsa pre are one line leading to one security stand) - the older days of choosing the security station was never fun.
Of course, I understand and empathize when a couple splits off into separate lines in order to increase their chance of faster service. When one member exits their line to join the partner, the line becomes one person shorter.
and boy would I love a single line system for entering Disneyland!!!!!