I personally think that women dress for other women, in order to compete for men. Because think about who judges outfits the most? It's women. Men don't usually care that much about what we're wearing and in general, I find, they prefer us at our simplest. I also think, though, that as women get older, they dress for themselves because they generally cease to stop thinking about what other women think of us because the majority are married with children.
Women generally compose their outfits on the following things: functionality and impression. Functionality includes dressing appropriately for the situation as well as comfortability, etc. while impression focuses on making an impact. Basically making someone think "wow."
The first thing, for example, that I think when I see a girl with a really cute outfit on is "what am I wearing? does it look in comparison to her outfit" I find that that's a common experience of many women.