A: Because no one knows what type of medical treatment you want more than you do!
Having an advance directive in place ensures that your wishes regarding your health care are carried out, even when you’re unable to make your wishes known. In fact, in the absence of a valid advance directive, some hospitals will adhere to the wishes of your next-of-kin (which you may not want!) or even worse, to protect themselves from liability, hospitals may require that an individual be formally appointed by the Court as the patient’s Conservator before they are willing to take directions from anyone other than the patient (and this court process could take WEEKS and be very expensive).
At the end of the day, an advance directive helps loved ones and medical personnel make important decisions during a crisis as well as long-term treatment in the event of an extended stay in a hospital or other facility.