Why does Sammy think of customers as sheep in "A & P"?What does Sammy's reference to sheep in the short story "A & P" by John Updike mean?

Sammy thinks of customers as sheep because he really doesn't care about them as individuals.  They are all the same to him...simply people that are there to buy goods.  Also, let's think about how sheep are regarded and taken care of.  They are not regarded as the smartest animals, first of all.  Also, they are herded through gates by Australian cattle dogs or other types of herding dogs, just as the customers are herded through the check out lines at the A & P store where Sammy works.  The reference of people as sheep is not a pleasant or flattering one, then, as we can see!