In my experience I'd say the ration of men to women is a lot nearer to 50:50 than you'd think, but to answer your question there seems to be people who feel that they always need their partners approval. Naturally these people would be attracted to a "dominant" character and vice versa. It's the old nature/nurture thing as well - are these people turning into the same person as a parent because of their parents' influence/behaviour or their parents' genes? I know this is a bit of a simplistic generalisation but it's a big topic.