Why do women raise their arms in the air and expose their crusty armpits(when sleeveless) in the face of a hot?

Why do women raise their arms in the air so much and expose their crusty armpits(when sleeveless) in the face of a hot guy. I am a somewhat hot guy and one thing that I noticed is that when a lot of women are digging on you they'll constantly be raising both of their arms in the air and putting their hands behind their head, and exposing their stank pits. Does it have anything to do with the pheromones that humans release from their underarms that signel ual desire. And this is not preening cuz I've seen preening(playing with yer hair) too. Another thing that I have noticed is that some girls like to ball their left hand into a fist and put it by their waist while simultaneously raising their right hand in the air(kinda like they do at male strip joints) around a hot guy. I had a cashier at a grocery store do that to me one time right in the open and it looked kind of bizarre. Anyways, any help would be appreciated.