It is often important information in order to make an accurate diagnosis or provide safe treatment. Illegal drug use is the most common.
maybe but say you robbed a bank and got shot. the fact that the bullet wound happened at the bank is kind of immaterial so that could be conveniently left out.
But no, I don't see any reason that you would ever tell your doctor that you are holding large amounts of bitcoin.
maybe if they are withholding some important medical treatment and need a proof you can pay?
So if you don't trust your wife to know about your bitcoin, do you trust her to know about your fiat?
telling a wife or trusted person some secrets always comes at a risk. by giving them that information they can become a target if someone else thinks or knows they know that information. it's not about whether you trust them but what type of situation it might possibly put them into. yes they can pretend they don't know anything but if your story doesn't match theirs then someone is lying. robbers aren't dumb. but in the end you do what you think is most reasonable.