It shouldn't be surprising, then, that the problem is primarily an internal one.
A statement that often accompanies women's complaints about not getting the men they want is something to the effect of "I know I am a catch. The reason for this is simple: your self-perception of your potential is roughly accurate, but you aren't living up to that potential. You know you can be a fun and exciting person to be around when you feel comfortable, but you haven't confronted your insecurity in social situations, so men don't realize this.
You know you have a great figure, but you haven't learned yet to show it off by correcting your posture, so no one notices it.
Your are well aware of your inner feminine self and you instincts to nurture and love, but you suppress them (as you've been implicitly told to do by your parents or the culture around you) and men assume you are cold and boring.
You know that you are an incredibly sexual person, but because of your strict conservative upbringing, you cloak it in "modesty" and men are turned off.
And the simple advice for women in this situation (which I have seen on other blogs, and have occasionally given out myself) is sometimes appropriate: "you aren't hot enough to get the guys you want; lower your standards." However, in most cases, I think there is deeper phenomenon at work.