I don't know why some bodily functions are considered so socially unacceptable to discuss. Like I get that some of them are gross - you wouldn't want to bring up certain things when someone's unwrapping a Baby Ruth, or phlegm when they've just cracked open a creme brûlée and are about to slurp down the yummy goodness inside.
But those are specific social instances where the food someone may or may not be eating has a strong correlation to whatever unsavory bodily function you're bringing up. Some bodily functions, for some reason, have been turned into awkward topics of conversation regardless of social context.
Menstruation is one of them.