I’m sure there are multiple reasons but here’s a novel one: alcohol inhibits men’s ability to distinguish between female friendliness and sexual interest. Doesn’t hurt their ability to tell the difference between conservative and provocative clothing though:
The current investigation examines the etiology of men’s errors in sexual perception after moderate alcohol use. Sensitivity and bias estimates, derived from multidimensional signal detection analysis, revealed that men’s alcohol-influenced performance was associated with declining sensitivity to the distinction between women’s friendliness and sexual interest. However, sensitivity to the distinction between conservative and provocative clothing was unaffected. Similarly, an alcohol dose led to an increased bias to respond that women’s ambiguous cues were sexual interest (rather than friendliness) but did not influence response thresholds for clothing style. Thus, there was specificity to the perceptual and decisional changes associated with alcohol use rather than a simple degradation of men’s capacity to process all dating-relevant cues in the environment. Given the link between alcohol use, sexual misperception, and acquaintance-initiated sexual coercion, understanding the etiology of sexual misperception in the context of alcohol use may inform sexual coercion prevention efforts.
Source: “Alcohol alters men’s perceptual and decisional processing of women’s sexual interest.” from Journal of Abnormal Psychology, Vol 119(2), May 2010, 427-432.