why a woman does not take cue in sex

While throwing this topic for discussion, I do understand that a man is a natural aggressor in sex. Most of the times a man initiates, pleads or in some cases demands(unfortunate though) the sex with his partner. (Mind you all, I am talking about straight sex, man to woman, nothing to do with other forms of sex.) While sexual desires are common, why a man alone should grumble(no offence meant to anyone) for the intercourse. There are no favors exchanged and both participants rejoice the interlude, relax soulfully and stay healthy, yet the man alone draws flak for something unpleasant...let alone the credit for the same go for a walk.
A woman is often seen veiled, less lusty in her outset, approach and attitude towards sex. Today the whole world, the techies in particular cry in unison that sex is healthy and is the major cure to stress, depression and other psychosomatic disorders. Besides sex develops a great understanding between the couple and develops an yearning for each other. Therefore in this light, is it only the mechanical grind that separates both of them or is there anything to do with the non-committal attitude? Most of the times when two young people (male & female obviously) fall in love, the proposal comes from the boy upfront. The girl merely accepts it or rejects. There is nothing that stops a woman in this modern world, why then back off when someone rises the topic of romance and lovemaking, more so in sex. Yes in sex.
P.S. I would like to listen to all sorts of comments from all, especially from women.
Disclaimer: This discussion is started with a good intention to deliberate the shyness or any inhibitions in girls and their general attitude towards sex. This article never intends to offend anyone concerned in anywhich way.
Thanks