why do women shave / wax their underarms?

I've never really understood this one either. I wonder when it was decided that women should not have as much body hair as men. I mean, we're expected to shave our armpits and our legs, but men aren't expected to do either of those things. *sighs* I know a lot of guys who get really freaked out when a woman has armpit hair, and think it's really unattractive, yet they have it themselves. It's a weird double standard.