They wouldn't have made the sign if it wasn't.
no, customers really are this retarded
Customer: Is this express?
Customer: Can i come on this line?
me: Do you have 12 items or less?
Me: so no
Customer: but i have close to 12 items or less (Referring to a wagon full of groceries)!
Me: But you don't have 12 items or less do you?
(conversation carries on for 5 more minutes)
and shit like this happens every single day.
It's less about consumers being morons and consumers being smart and arrogant. Pretty much anyone shopping can count to 15. Express lane rules are rarely enforced and without enforcement, a good number of people will never follow the rules.
This sign is about trying to make people feel stupid for breaking the rule, but will likely fail since at the end of the day it takes less time to just ring the rule breaker up than sit there and argue with them.