Who gets to decide what the patient's wish is? As we saw with Terri Schiavo, it isn't always the patient who decides. A rogue judge can easily decide that a patient wants to commit suicide, even when there is strong evidence against such a ruling.
Speaking from someone who is always in pain and suffers from depression what I might want one day may not be the same as next week. Things like this always start out one way then change and the next thing you know anybody but you is the one making the decision if you should die. Birth control was suppose to make abortions go down?