Coping mechanism for socioeconomic factors not unique to but most prominent in the US.
Watching TV in America is nothing but a continuous flow of commercials about symptoms and diseases that they really want to convince you that you probably have. We know advertising can make you want all kinds of things, so why not symptoms and diseases?
Funny fact, any commercial for a drug, here in Romania, is ending with a very fast auction-style warning that last less than 5 seconds. In US you have like 5 minutes of country music and elder people having a picknic while all the possible dangers in the world are softly planted in your mind. :)