Because all women have different taste, men need to approach a large number of women that they find attractive in order to find one that reciprocates that attraction.
This requires serious balls, thick skin, and persistence. In general, a man has to get rejected many more times than a woman in order to succeed at dating.
She has to wait until another man (that she likes) approaches her.
The cues include facial expressions, hand and body movement, physical touch, voice pitch, voice sounds (not the articulation of the words), physical appearance, emotional appearance (like teary eyes), and even smell.
I did not realize how often I used non-verbal cues to communicate until I started dating a non-Hispanic girl who once asked me why I smacked my lips and made other sounds to convey my feelings, instead of simply expressing them verbally.
A woman has to have the courage to let the man walk away, while a man has to have the balls to approach in the first place.
While men have to become confident enough to approach without knowing how a woman will respond, women have to become confident enough to let a man act according to his true feelings for her, without knowing whether he will stay with her or leave.
I've dated countless women and it has always amazed me how little they know about men.