Because of poor-but-good-intentioned and outright malicious reasoning about gender in laws. The idea is that women would be too ashamed to press charges because

Because of poor-but-good-intentioned and outright malicious reasoning about gender in laws. The idea is that women would be too ashamed to press charges because of social stigma however being accused of a crime carries no social stigma at all -- see the Duke Lax case for an example of how the accused are treated fairly.