To show off - and attract. Attraction, however is not best on looks . It is the confidence one exudes and personalities exhibited. Showing off (as my those who should know better post proves) does not work
But this is a sexual thing. It is not something like them making their hairs. I hope you are aware of that. But you are not saying that their purpose is to attract handsome, muscular guys and have sex with them. Are you? I don't really get the point of making yourself a sex object.
It's about presentation - In order for any person to attract, then they take the time to prepare themselves in the best way they can - Primarily: For themselves, how they feel themselves and are compfortable in Secondary, in order to catch the eye of the many - so that selection can be from many and the various
It is a sexual thing for you. To them it is a pair of shorts. They don't need a reason or excuse to wear what they want to wear. Also, your urges to masturbate are 100% your lack of self control and has nothing to do with what anyone is wearing.
Both men and women flaunt. All animals do it. Some people flaunt their bodies, some their money or other possessions, some show off talents or abilities, or engage in risky behavior. It's instinctual. Everyone tries to get attention, at one time or another, for any number of reasons. Thing is, no one necessarily wants everyone's attention all of the time.
Whatever the ladies wish to reveal--just enjoy. (in fact you must enjoy what you seem to deride-----otherwise you wouldn't be bothering your pecker so much.)
Personally, I can't see how the ladies can stand thongs, shorts, etc jammed up in "there", but I'm so happy they can!!!!