I've come to the conclusion that they don't really expect men to know, but it's a all a tool to make men feel guilty.
I believe that, when in school they split the classes to go over sex education, while they were showing the lads how to put a condom on a cucumber, they were teaching the girls how to mess with men's minds to manipulate them into guilt via confusion.. and so long as there's a woman on the throne that will always be the way!!