According to the old swamper, why does Curley wear a work glove on his left hand?

In Chapter Two of John Steinbeck's novella Of Mice and Men George and Lennie come to the ranch where they intend to work and initially meet Candy, the old swamper. Candy describes some of the characters on the ranch, including the boss, Crooks, Slim, Curley's wife and Curley. Curley is the boss's son and Candy claims that Curley is a fighter who competed in the Golden Gloves' boxing competition. He also suggests that Curley likes to pick on guys who are bigger than he is to prove his manhood. Moreover, Candy tells George that Curley wears a glove full of vaseline, apparently to keep that hand soft for his young wife (George refers to her as jailbait). This is a somewhat sexual image which leads George to tell Candy, "That's a dirty thing to tell around." It is the same hand, a symbol of Curley's masculinity, which is later crushed in the bunkhouse fight with Lennie.