Smart millionaires keep their mouths shut and their purchases private. If I hear someone bragging about money, it is typically because they wish they were rich. IMHO.
Not all the time. Some people just overcompensate and think that money = success and they need to let everyone know how "successful" they are, but a lot of people also do brag about money they don't have for this exact reason.
You're also forgetting the fact that many wouldn't because it would immediately make them a target.