Curley's Wife is the only character in this story whose real name is never revealed. There are potentially many different reasons for this, but the most compelling argument as to why Steinbeck chose not to reveal her name lies in his presentation of women and the way that they were treated and thought of by men at the time when the novel was set.
It is interesting that Curley's Wife is a character who is shaped for the audience before the audience really gets to know her. She is called a variety of insulting terms by the men in the bunkhouse, who basically accuse her of being a prostitute and "having the eye." Yet, it is only when Lennie gets to know her that she opens up, and the real character behind this title is shown to the audience. Far from being a superficial flirt who is a loose woman, Curley's Wife shows that she, just like the other characters in the novel, once had a dream that is now destroyed and that she is intensely lonely:
I get lonely... You can talk to people, but I can't talk to nobody but Curley. Else he gets mad. How'd you like not to talk to anybody?
Steinbeck slowly develops the character of Curley's Wife, first presenting her as nothing more than a whore, but then revealing her to be a woman trapped in a hopeless position, to challenge the reader's assumptions of her as a character. Just like the men in the bunkhouse, the audience is tempted to dismiss her character without giving her a chance. She is called Curley's Wife as a reflection of the way that she has no identity outside of her relationship to Curley, and that her powerful character and restless dreams are forced to be subsumed by his character. Calling her Curley's Wife alone is a powerful way to communicate the pity and sympathy that Steinbeck wants the audience to feel towards her.