No, it most definitely isn't. I'm originally from the US, by the way. The midwest, if that helps. Some families will talk about it, others don't, and a lot will pass on talking about it if it was 'no big deal'. So the weird mole? Yeah, you probably didn't hear. You especially didn't hear if it was your cousin. Not everyone will talk about their prostate, especially folks more embarrassed about bodily functions or anuses. A lot of prostate cancer doesn't require treatment, after all, and no reason to talk about it. If your great grandmother had cancer, you probably don't know, especially if she died from a heart attack or stroke. Doubly so if your parents and grandparents are still alive and have not had cancer.

And yes, I've met all sorts of folks like this. I worked in a pharmacy for years.

You just assume everyone will talk about such things.