Why are women obsessed with their thighs?

Most women I have dated have made it a point to show off their thighs. They'll say, "I used to be a swimmer" or "I used to be a cheerleader". They will have me look, feel, and seem to need my approval. When we play tussle in early courtship, the legs always have to work their way into the play. I will either get a foot on the face, a playful body scissor while we're on the couch, or a full on head scissor just to assert strength or some sort of lower body dominance. Are females so touchy about the thighs that they need approval or do they know that some of us males are so turned on by female legs that the mere touch, site, or constriction will turn us into putty? Regardless, showing off legs took place in probably 90% of my dating experiences from teenager right up to adulthood and I am wondering why.