I agree that ignorance of other peoples’ experiences isn’t a blameworthy thing. But it does demonstrate one reason diversity is important. A smart person acting in good faith can miss things that are completely obvious to people with different life experiences. We all only know what it’s like to be us.

It's such a basic question that it would be better to do an internet search or read the wikipedia article on the topic. You might as well ask why heart attacks are a big deal.

I might as well ask what are heart attack apps useful for. I wouldn't know what are heart attacks apps for.

Strange/stretched comparison. Menstruation is all about the cycle. Even as a man one would/should know because the basic methods of avoiding pregnancy when having sex should be of interest to men too. Because of the importance of that cycle its also indicative for a woman's health in general (lots of hormonal changes within the cycle; regular blood loss too).

Heart attacks are just point-events on the other hand, they happen and that's that. So knowing full well what a menstruation app is useful for one would still not understand what a similar app for heart attacks could possibly even mean. Calculate your heart attack window? That would be something new indeed, so you are right not to see the point. Just as there is no point in using heart attacks to understand the menstruation cycle.

Plenty of other people already explained. I decided to leverage this as a teaching moment.

Thank you for the kind lesson. I genuinely didn't know.