Because girls are not boys, or to put it scientifically, for the human reproductive system to work you need both male and female. If girls weren't girls the human race would die out.
girls,girl's,girls'
it would be:girls'girl's andgirls
Motley Crue
The 1962 film starring Elvis Pressley was Directed by Norman Taurog. HAHA PRETTY LADY!! SAYS ELVIS