Curley's wife does not have a name because she does not have her own identity. She is just Curley's wife. She has no real sense of purpose. She does not fit in with the ranch hands. She lives a lonely existence. She has no friends:
Curley's wife (as the boss's son's flirtatious wife, she is not identified by any other name) wanders around the ranch searching for some human contact.
All that Curley's wife has is a dream. She is really considered a nobody. She has always dreamed to be a somebody. Sadly, all she can do is dream. Because of the isolation she lives in, she has no chance of ever making something of herself:
...she is pathetically lonely and had once had dreams of being a movie star. Both she and Crooks crave company and 'someone to talk to.'
Sadly enough, she is so desperate for attention until she reaches out of Lennie. She is flirtatious because she desires to have a name and be someone with a worthwhile purpose. In the end, Lennie accidentally breaks her neck. He too was reaching out for attention. She dies without a name. She is nameless because no one cares to know who she really is. The ranch hands have their own lives and she does not fit in.