The point of the hijab is to NOT hide a woman's beauty. Its a sign that god is above. As well as doubling as protection from the sun. Its the same as a jew wearing a Kippah or an orthodox Christian woman wearing a veil in church.
If it sufficiently hid a woman beauty than the burqa (which is mean to conceal) would not be needed.
Your original assumption was wrong, and that is why it made no sense.