Curley's wife and Crooks share one important characteristic - powerlessness. Within the social hierarchy of the ranch, these two occupy the lowest levels of status, importance and freedom.
...the theme of loneliness is further explored in the solitude borne by Crooks and Curley's wife... Both these characters crave company and, as Curley's wife says, "someone to talk to."
Curley's wife is expected to stay in the house all day. When she fraternizes with the men on the ranch, she is rebuked and becomes the target of both fear and derision. The men cannot trust her and say that she is a "tart", which may be true, but she is also isolated and lonely and sees no positive way to achieve a social life on the ranch.
She once dreamed of being an important person, a movie star. The notion that she could have been a star remains important to her despite the fact that the man who said she could have been a star was lying to her and, ultimately, she knows that he was lying.
Crooks is also isolated and expected to stay in his place which is well-defined both socially and physically. As a crippled person, Crooks has little literal power and this mirrors his social position.