Watch the full ad for a spoof of every tampon commercial ever. They are absurd (basically the ad industry is in denial).
America, for one. Sure its too a lesser degree, but taboo still.
Where I live in the US it is no more taboo then urinating or defecating.
My female friends (and girlfriend) are all okay with saying they need to pee. However, they will never say something like "I need to change my tampon". If they do, it will be directed at 1 person in hushed tones and because they're out or something.
Maybe yours are different though.
Isn't that just courtesy? I've found the topic tends to really gross guys out (much as uniquely . . . male things gross out girls), so it's best avoided in mixed company.