To be specific in secular culture guys are not expected to be chaste. In Christian culture we do not have that double standard.
Let's get some historical context for Purity Balls and the rest of it.
Way back when a woman who had sex out of wedlock was likely to get pregnant due to the fact that the only contraceptives available were made from iffy home recipes. It was provable that she was pregnant, but often the man could get off scot free, unless he was honourable and stepped up the plate.
A man could have sex without much reprocusion. Any evidence that he had had sex would be put down to a "he said - she said" battle, and the woman would likely lose, as women were seen as weaker, lesser creatures.
Way back when balls were often done with the intention of showing off daughters so that those daughters would get married off. Those girls would get married off to middle-aged widows, often friends of the girl's father.
So, then, to modern purity balls. To get down to brass tacks, the teenage girls are being shown off by their fathers to other fathers, and are being shown to be clean, honourable virgins.
However, it would seem that the balls themselves are little hypocritical. Showing of girls in pretty gowns, girls who are pledging virginity until marriage! Not only does it reduce those girls to little more than property but it also doesn't do much to actually prevent pregnancy.
Putting those girls in ballroom dancing lessons, or in softball teams, or in ballet or music lessons or language clubs, now there is a way of assuring that a girl becomes a responsible, well-rounded person who will make the right decisions when the time comes! Giving the girls power over themselves to make the right decisions is a much better way to prevent sex than to leave the decision up to the father!
I think the fact that there are so few mother-son purity balls is a throwback to the time when mothers were to be "taken care of" by their sons, when women did not have personhood. It's backwards thinking, to be sure, and shows that we haven't yet come far enough, baby!
Women and men are now both "persons" Women are able to use their talents and strengths to earn careers, and they no longer need sons to "take care of them". And, of course, daughters are now able to use their strengths to help out parents just as much as sons if the need does arise!
