Well, from a historical perspective, did you know that in the Victorian era -- the golden age of "female modesty," prostitution was far more widespread than it is today, and was socially acceptable to boot? In many parts of the country, it was considered the norm for a father to take his son to a prostitute as a rite of passage.
Because most of the regular women shunned casual encounters.
What does THAT have to do with female modesty?
Girls in a Middle America area like the Cincinnati Suburbs dress like porn stars when they go to school. Back in the day (mid 1970's), porn stars were just getting started themselves. I also don't recall "rainbow parties" taking place in the 1970's either -- certainly not at junior high age!