Politeness on the part of the staff is valuable. People go where they feel prized. When they are treated as annoyances, when people snap at them or ignore them, they stop coming.
Why pay to be treated like dirt when one can get that for nothing?
One has to find out how each member of staff talks to the customer. Don’t just focus on the ‘front line’.
Sometimes a customer might ask a worker a question. If he is rude the customer is gone.
That it ‘isn’t his department’ or that he was ‘busy’ doesn’t compensate for the loss of custom his behaviour has caused.