The reason men find women more attractive in high heels has its basis in biology. High heels make the legs look more tone, which gives the illusion of better health and more fertility. Men don't realize it, and women may rarely think about it, but the human male is attracted to females who show signs of increased fertility. Along these lines, high heels also accentuate the arch in the lower back, they contract the gluteus muscles which emphasize the derrière, they tilt the pelvis forward, and lengthen the legs. All these characteristics are consistent with increase fertility - thus increased attractiveness.
High heels also make a woman's feet appear smaller, which while not a biological driver of attractiveness, is common to many cultures.