Many women struggle with the concept of submission. They assume that men think like they do, that men respect and are drawn to shows of strength and independence and look down on displays of weakness, fragility, and dependence. Nothing could be further from the truth.
The other day I was out walking with two little girls and two very large dogs that outweighed them by a considerable amount. One of the dogs belonged to one little girl, who was naturally not in the least bit afraid of either of the brutes. The other little girl, her friend, was somewhat afraid of dogs in general, so she was naturally a bit nervous to be in the vicinity of two such oversized specimens.
I didn't really know her, nor am I the sort of man who particularly likes children that are not his own. However, when the dogs began playing with each other, barking, and charging back and forth, I felt a little hand slip into mine.
What I found interesting was that I immediately felt an instinctive sense of responsibility for her that I had not felt the moment before. Not that I would have ever permitted the dogs to harm her; the reason I was present on the walk in the first place was to ensure that the beasts didn't get out of hand in case we ran into anyone else. But her gesture was a request that said: "I'm scared, please protect me", to which the normal male response is to feel more affectionate and sympathetic towards the individual for whom he has accepted the responsibility of protecting.
This is why young couples often like to see horror movies together. It is an emotionally bonding experience, as the girl seeks the feeling of being protected and the boy has the opportunity to assume, however hypothetically, the role of her protector.
Because women don't think like men, they don't understand that being challenging is intrinsically unattractive to men. It provokes the man's fight (or flight) response rather than his protective response, but since in most cases the man actually doesn't want to fight, it leaves him feeling frustrated and conflicted. Being submissive, on the other hand, provokes a protective response, and the subsequent affection.
So, if you are a woman, consider what sort of response you wish to provoke in a man. Do you wish him to feel more affectionate to you or less? Because that is exactly the choice you are making when you decide to behave in a submissive manner or not, regardless of your intent.