How old are you?
Fathers are hesitant and income about realizing their daughters have become sexual women and/or he is no longer required to be there to protect his child as he could when they were young.
Part of what they saw as their job is gone
However, at some point a woman goes out and starts her own life. I don’t think there are too many fathers of let’s say 30 year olds that are surprised their daughter is having sex.
Those t shirts? Those are jokes. But you must have realized that.
I don’t think many parent like to dwell on their fact their offspring are doing with someone the same things he and their mother do in bed.