I wonder how anyone could consider anything "sacred" outside of a religious context. Being an atheist, and anti-religion as well, I consider life to be precious, but not sacred. And each person's life is most precious to herself. But, whether you regard it as precious or sacred, what is the benefit to anyone in keeping alive a terminally ill person? Giving them drugs to mask the pain might make them comfortable, but eventually the level of drugs required makes them no longer a person. What possible "sacred" motivation could there be for keeping them alive, especially against their own will.
Not going for sympathy here, but I think my own experiences help to illustrate this very well. In 2012 I lost both of my parents, seven months apart. As I've mentioned before, Mom had a rather nasty combination of Alzheimer's and Parkinson's, along with a few other physical health issues. By the end of 2011 there was very little of my mother left in her body. She seldom recognized any of her children, and by the final weeks could no longer recognize my father, her husband of 63 years. The doctors could have kept her alive, feeding her through a tube (she could no longer feed herself). But, as my father said, "What's the point? Her mind is already gone. Let her body go, too." She had a living will, prepared well before she began to get sick, and the hospital honored that. She was gone within a week. And, as I said, her body was virtually an empty husk. There was nothing of my mother in there.
Seven months later it was dad's turn. Cancer got him, a cancer he had been ignoring so he could help my mom. It spread to his spinal column and became inoperable. He was in tremendous pain. They could have given him chemo, and radiation, and whatever else they dreamed up in a futile attempt to save him. He said no, he was ready to die. They put him in the hospital, gave him pain meds, and we watched him die. We were sad to lose him, of course, but having seen how miserable he was after losing my mother, and how much pain he was in from the cancer, there was no reason to refuse his wishes. He was 85 years old, and ready to die. We let him. And, as I've noted above, by the time he died the drugs had taken away his mind. To my mind, he died several days before his body gave in.
Now, I can understand that someone who is young, and with a long life ahead of them, potentially, should be treated differently, in most cases. But prohibiting someone from controlling their own life, or death, is no different than slavery. Doing it in the name of some imaginary being who has a fetish for torturing people doesn't make it any better. I read, or heard, someone this week who said that, when the early religions began to make the afterlife seem so pleasant, far more pleasant than the lives of most of the people, a lot of people began to take their own lives, deciding things would be better in heaven, so why wait? So the shamans had to come up with the idea that suicide was a sin, because the gods wanted you to suffer, or something. Basically, people who are dead don't give money to the priests, so keep them alive as long as possible. Nothing sacred about life, just more bodies for the pews. It's emotional and mental, and sometimes physical, slavery. With all too willing slaves.