I've a very solid hypothesis, just needing validation from neutral contemporaries to justify it as a theory so without further ado, my latest generalization that will most likely offend you:
Only unattractive women make the first move because they're scared of dying alone. Attractive women don't make the first move because they don't need to: guys will hit on them and within a week, they'll have a stable of studs and duds to select from.