Why is it that some say girls "don't respect themselves" when they are promiscuous?

I would argue very strongly that allowing tradition to effect the way you live your life is disrespecting yourself. I have never, in my entire life, heard an intelligent argument in favor of following traditional rules. They have no known purpose other than establishing who is in charge, and that by highly unfair and inegalitarian methods, like gender, race, birth order, etc. putting that nonsense above your own personal happiness is extremely disrespectful to yourself. If having with a wide variety of men makes a girl happy, how can she possibly be considered to be disrespecting herself?