Yes

You look around to a close park and see a man about in his late 50s, maybe 60s talking to a girl in her 20s with curly blonde hair and a shaven pussy before the two beginning fucking like wild animals. There's your answer.

"Uh, excuse me." You say calling attention to one of the sorority girls, an Asian girl with a pony tail. "Would it be odd to ask why all the women as bottomless and there's casual sex?" You ask.

She laughs for a bit, before seeing you were serious. "Oh, I'm sorry, you must be foreign, right?" She asks. "Something like that." You respond.

"Well, over a hundred years ago, after great casualties in World War 1 and the population greatly declined, we passed a law in America that all women served to reproduce with men in any way convenient. Over time the law grew to include going bottomless in order to more easily accommodate men and also for sexual pleasure of men, not just reproduction." She explained.

Intresting. I'm sure no one on my Earth could have predicted that suffering heavy losses in the first World War could have lead to pantless women and public casual sex.

"So, do you want to have sex right now?" You ask her. "I'd love to, but me and my sorority sisters are busy at the moment. Maybe you could use one of the other women around here and then swing by the sorority tonight?" She offers. Sounds like a plan.