Curley's wife plays an important role in the novel and yet is never given a name. Perhaps Steinbeck was trying to not encourage the audience to develop a personal connection to her? I'd like to see various other points of view, supported by textual evidence.
According to this NYT Article, Steinbeck's wife Elaine asked him this very question.
His answer was:
"For one good reason. She's not a person, she's a symbol. She has no function, except to be a foil – and a danger to Lennie."
The article was written by Jay Parini, who also wrote a biography about Steinbeck. Since there are no references in the article, I emailed Parini to see if he could remember where he got the quote from, but he could not.