What's the point of the hijab and why do Muslim women wear it?

What's the point of it? I've been reading in the newspaper a lot lately of issues women are having with employers/governments because they wear a hijab. Wouldn't it just be easier to take it off while at work and only wear it on your time? I mean, if I can't wear a hat because it's against company dress code why do Muslim women get to wear a head scarf?