Knowing a bit about this subject, some people who are suicidal will left-handedly ask others for permission. To have a doctor be in the position of possbly assuring a person that it's all right to kill his/herself arguably violates the Hippocratic Oath.
I can certainly understand the compassion of not wanting someone to be left to suffer needlessly when they no longer have any chance of a productive life. I think that a line has to be drawn when it involves other people participating in that decision and process. Whether a life is worth living must be left to the person themself alone.
..."...the compassion of not wanting someone to be left to suffer needlessly when they no longer have any chance of a productive life."...