I have an idea why there isn’t discussion. It comes from the vagina, something many people hate and fear. Part of the stigma is that it’s blood and that it has a scent, which makes people think it’s dirty. Not to mention religion has done a great job of stigmatizing it as a punishment or curse. Once I found out about it, I wondered why it was so hidden and talked about so little/ I remember being told about menstruation by my mother and in class but never about what it meant. I had no idea about blood, pads, tampons or anything. It’s easy enough to know that an egg moving but nothing about what happens. It took my first girlfriend to explain it to me and she was amazed that I wasn’t grossed out by it. It’s just as natural as breathing and sleeping.