Some women think balls have urine in them, it's hard to magically know everything about a body that's completely different from yours. Sure it's only a Google search away, but if it's something you never think about then you'll never think to Google it, especially if you have no reason to doubt what you already think.
Idk how things are done in mother Russia, but in the US they're very weird about teaching stuff like that. Half the time they'll split the boys from the girls and teach each group only what applies to them. On top of that, the US education system is a joke overall, so nobody's paying attention in that class anyway. The few kids who are paying attention are laughing every time the teacher says "penis"
Basic health education in the USA requires to learn basic anatomy like penises and vaginas and organs like bladders and milk ducts. We are required to take biology classes in high school and while health classes in middle school and high school is run up to the discretion of the school district and can be separated, the basic information is still taught in biology in high school.