Why do consultants write such scary, incomprehensible letters?

There is a kind of letter designed to bewilder, upset and possibly terrify its recipient, and this is the standard letter sent by specialist medical consultants to the victims of disease. Actually, the letter is usually addressed to the sufferer’s GP, but a copy is always sent to the patient as well; and because of this it usually begins with a flattering personal reference just to soften him up (‘It was a delight to meet this charming old gentleman’, or some such phrase).