Men do not act differently just to impress women.
Actually... very often they do. Sexual dimorphism isn't so pronounced in human beings as it is in, say, the peacock vs the peahen, but it's still there. And men quite often strive to impress women. Whether he's dropping names at a Hollywood party, letting a Rolex(tm) dangle off his wrist, making a slam dunk, or getting into a fight at a bar, a man's behavior, in the presence of women, is frequently predicated on the desire to let those women know he's a desirable mate.
Another way of looking at it is this,
pretty women make men stupid.