I think anyone who's watched a loved one suffer needlessly understands that there should be better options.
I really don't understand why anyone would oppose the concept of death with dignity. Is it just a personal fear of dying? Mistrust of doctors and family who might have evil intent?
I know some have mentioned the fear of making a mistake. I get the point. But it seems to me the risk is very small, compared to the very large risk of being kept alive, suffering and with no prospects for any quality of life ahead.
It also seems a little selfish. I've always tried to contribute something to the lives of friends and family, and to society in general. When I can no longer do that, my job here will be done. No need to hang around just to prove I can keep breathing, as some kind of a living trophy to medical science. No need to burden my family.