Men are pigs - well most are.
And I've really come to notice it with my daughter now ready to turn 17. I've known my wife for 23 years. I always noticed that other guys would stare at her - but it was different as a boyfriend/girlfriend husband/wife thing. I always knew I had her at the end of the day.
But, my daughter is a different story. I know I can't really protect her - I can only teach/guide her to protect herself, because I can't be with her all the time. But when we are together, I notice ALL ages of pigs (oops, men) staring at her, and not just idly glancing, but that drooling sort of stare. But mens hormones are sometimes pretty powerful. A year or so ago, I was outside waiting to pick up my daughter from a dance, and I was wqiating with several other fathers. Many girls were leaving the dance - all at the age of our own kids. We all looked at each other, and commented how these girls looked, and how we could envision others staring at our daughters in an unhealthy way.
You could start a whole other thread on how guys react to how girls dress, but a lot of teenage girls do look really sexy - period. Can't take that away from them. But why do some men think that "look" gives them carte blanche to touch, etc?