In "A & P" by John Updike, why would the setting matter to or affect Sammy's actions?

The story is really about young men’s fascination with young girls. Updike was an art student before he became a writer. His visual sensitivity is apparent in his stories. "A & P" is a picture of a supermarket in a small resort town. He brings the three girls into the store to create drama. It is definitely “small-town” drama. The drama is only there to intrigue the reader—but the real purpose of the story is to paint a picture. Without the three girls the piece would be just a sketch. It would be hard to interest a reader in a simple description of the inside of a small-town supermarket in the middle of an uneventful summer day. The girls also give a visual focus to the work because Sammy's eyes follow them around the store, up and down the aisles with which he is so familiar. The title of the story suggests that this is not so much about the people as it is about a typical American supermarket.

Updike's story is especially valuable in that it demonstrates a truth about writing. It is easy to get readers to visualize things they are familiar with, and very difficult to get them to visualize things with which they are not familiar. That is why there are so many analogies, similes, and metaphors in poetry and prose fiction. That is why we ourselves us so many analogies, similes and metaphors in our own conversation.

Updike's task was easy in "A & P." We have all seen supermarkets with their aisles loaded with colorful cans, packages and bottles. We have all seen those shoppers pushing their carts up and down the aisles and then lining up with such docility at the checkout counters. We have all seen women like the one in the story who watches the cash register hoping to catch the checkout clerk in a mistake. We can easily visualize the store manager because they all look so much alike, dress so much alike, and seem to be trying to be visible and invisible at the same time. And we can visualize those two boys checking out the customers and checking out those three girls. We have all seen girls like the ones Sammy describes, and we have seen them in bathing suits, bold and self-conscious, walking gingerly in their bare feet--but not usually inside stores, even today! 

I don't think we should attach too much importance to the happening but should enjoy the experience of being transported in our imaginations into a little world for a few moments. We feel sympathy for most of the little people involved, including Sammy, the store manager, the shoppers for whom this trip is the biggest event of their day, and for the three girls for whom this big adventure will end in success and embarrassment. It is a Norman Rockwell kind of setting, with Norman Rockwell characters, and even a Norman Rockwell message about life in the United States.