Girls Or Females as the word I would use for this question, have broad hip to facilitate child birth not to look attractive. If that looks attractive to you its your brain or mind that sees it this way.
Females need more space for the child to come out. As human body is erect unlike other mammals its Hip becomes small. That is the reason child birth in Humans is difficult. Males are OK with small hip but Females need Broad hip. That is the evolution
