often seen in the street without a hat

I have seen quite a bit of US high school films and TV things, and it seemed very odd to me too. Also, are you allowed to organise events which are only open to girls with dads? What about boys, can they dance with their dads if they want? I mean, surely they can, otherwise it would be suggesting that it was weirdly incestuous for the girls to do it rather than PERFECTLY NORMAL.