Fawahish And Sad-e-zariya
To show cleavage or thighs is still considered somewhat immoral or indecent and seductive in every culture including the West, and a dress that covers more is considered more decent. That is why you do not find, for example, a woman in some executive position wearing a revealing dress. Such dresses are not supposed to be worn by a Muslim woman who cares for her religion and her God and the day of judgment.