Great question, I'm a Muslim and wear hijab as well. Muslims are commanded by Allah (God) in The Quran to protect themselves by dressing modestly
“Say to the believing men that: they should cast down their glances and guard their private parts (by being chaste). This is better for them.” Quran 24:30
“...and not display their beauty except what is apparent, and they should place their khumur over their bosoms...”
So basically Muslim women cover their beauty to those that aren't close.
