Women proposing to men is not socially acceptable. Why not?
social norms and traditions - men do the proposing, not women, and that's the way it's always been.
Changing the rules changes the game. Many people believe that changing the way things are done (women proposing to men as opposed to men proposing) would mean changing the whole idea of marriage (with men being the breadwinners and women being the subservient housewives).
There is some kind of fundamental attachment between gender identity and social actions (like proposing marriage).
A man is a man if he proposes marriage. A man feels emasculated if he is proposed to by a woman.
Women think it's weird just as much as men do.
Women suffer from "princess syndrome" in which they wait for a man to come and save them, rescue them. A princess isn't impulsive or aggressive. A princess waits for her prince to come get her and get down on one knee and propose. This is in large part due to the media - commercials, television programs, movies, etc.
Disney alone sets the example for how girls should be when they grow up. If a little girl wants to be a princess, she gets the message that she needs to look pretty, keep quiet, not be smarter than the prince, be patient, and wait for the prince to come and save her. Then she can be a good princess when she grows up. These little girls would never do the proposing because it goes against everything they've been dreaming of their whole lives.