There were girls behaving exactly like this in my high school in the seventies. You saw only what you CHOSE to see. Yeah they hid it unless they decided not to get an abortion but the behavior was the same.
I had very little success with the ladies.
My friends had very little success with the ladies.
Friends of friends had little success with the ladies.
I knew girls -- they weren't getting much action either, because they were careful and picky.
This was in Boston, at the height of the Disco era, before AIDS.
The way people approach sex today is different than it used to be.