Dexter doesn't like being called "boy" because it makes him feel like a little kid. It's also a reminder that, despite everyone's praising his skills as a caddy, they still look down on him as a social inferior. Dexter may get on very well with the gilded elite with whom he rubs shoulders at this upscale country club, but there's still an enormous social gulf between himself and the patrons—a gulf which is reflected in the condescending use of "boy."

Dexter knows that he'll never truly be accepted as an equal by the high-rollers at the country club. To them, he's just a servant with a bag of golf clubs. His infatuation with Judy, then, comes in very handy, presenting him with a golden opportunity to assert his independence and leave behind a job that's become increasingly degrading.

In "Winter Dreams," Dexter's being called "boy" in part causes him to stop caddying because he decides that he's too old to caddy any longer. At least, that's what he tells others around him, like his family. However, Dexter has become smitten by Judy Jones, and it is clear that she is of a much higher social class than Dexter is. Dexter is ashamed of his lower-class status, and being called "boy" reminds him that he is just a caddy, expendable in the eyes of the rich men playing golf on the range. He is so overwhelmed by his infatuation with Judy that Dexter decides that the only way to get over it is to resign suddenly from his position as caddy; in other words, a sudden resignation would "cancel out" the sudden infatuation. Dexter's being called "boy" catapults him into his resignation.