Why? Because their word is so often at odds with their other words. Consider this fascinating pair of recent assertions by
I can’t flirt for the life of me either.... I’m a champion flirt when I want to be.Now, this particular example turned out to be a bad one, (the second woman was apparently quoting a different woman in the first part), but the topic is worth contemplating even so and I'll replace it later with an actual self-contradiction when one inevitably surfaces. I'm not sure what the reason for this tendency towards self-contradiction is, but my impression is that a) it begins at a very early age, as I've seen it exhibited in girls as young as three, and, b) it features some sort of connection between the expressed female perception of reality and the way that she wishes others to perceive her at the moment.
What I find remarkable is that if questioned with sufficient delicacy, a woman will often admit to simultaneously believing two intrinsically contradictory things. This may help explain why women are very credible liars who nevertheless tend to unnecessarily expose their own lies over time. If they actually believe what they are saying in the interests of convincing their audience of it, they cannot have any awareness of the fact that what they are saying now directly contradicts what they told someone, sometimes that very same audience, previously.
If it feels true, it is true. But since feelings change, what is true now is not necessarily what was true before. So, if we apply that concept to the obvious contradiction presented by Susan's commenters, and combine it with what we know to be the female tendency towards negative communication, we can retroactively "read her mind" to a certain extent.
"I can't flirt for the life of me either" = I don't want women to think I am shallow, submissive, or overly obsessed with pleasing men like those flirtatious women are."
"I’m a champion flirt when I want to be." = I don't want women to think I am incapable of influencing my husband in a feminine way at will.
Notice that there is no contradiction between the two negative desires. It is the process of translating the negative wish to the positive assertion that produces the contradiction. So, in addition to being useful in the avoidance of acting on false information, observing these contradictions and understanding what lies beneath them can serve as a useful window into a woman's mind. Or, on occasion, two different women's minds.