why do you think muslim women wear a hijab and cover up?

Many reasons: religion, social pressure, fear, and other I probably haven't thought of.

Fashion victims.

I'll tell you why. It's because of the way men in that religion have interpreted the part of the Quran that states that both men and women should cover the parts of their bodies that cause impure thoughts. Honestly, if they could, Muslim men would enforce a law saying women should also cover their eyes.

Skin protection seems a possibility.

Cause their men are insane