This may seem strange but many MANY women just don't "get" how their appearance appears to men. It may seem like they just don't care, but that would imply that they understand they look like they aren't making an effort. But instead, I think they really don't "get it". They don't know how non-sexy birks look (and sweat pants, flannels, etc). They just think they are dressing comfortably and they don't realize they are taking their own sexy away with these things.
(here's where I would get bashed by the gay community, but since I doubt any of them are reading here...)
In my experience, lesbians have the biggest and strangest problem with this. I have met many lesbians who love very feminine women, and yet they wear men's shirts, birks, baseball caps, etc. So if you ask them "well, don't you want to be attractive in a feminine way, the same way that you are attracted to feminine women?" they will simply get insulted and up in arms about how the feminine ideal is based on what straight men think it is and how insulting it is to be expected to dress for straight men's approval. And yet...the same woman is attracted to the same feminine women that straight men are attracted to. There is a lot of variation in this because lesbians can be attracted to an entirely different type of feminitity, but in general, they will still be attracted to full on girly girls.
When the Britney/Madonna kiss happened, every lesbian friend I have sent me the link to the video clip of it along with a "oohhh baby, so hot!" And most of these women wear birks!
