The initial reason is still valid. It wasn't that long ago that people got body lice at Camp Pendleton during the rifle range portion of Marine Corps boot camp.
As far as shaving women's heads... there are some times we do not need to be equal. After boot camp a guy with a buzzed head can go about life normally. A woman would have issues going about day to day life with such a haircut. In fact it isn't allowed due to the eccentric nature of shaved heads on women.