From a personal perspective, speaking as someone who has incurable cancer, and having been told by the professionals that (and assuming I don't get hit by a meteorite or a bus first) the end stage of my illness will probably involve hospitalisation and significant pain control since I have tumours in my bones.
I would at least like the option of euthanasia at the point where my survival could be measured in a handful of weeks, and where those weeks would gradually become more unpleasant for me and more distressing for my family. I can't see that there can't safeguards that limited the euthanasia option to people in my position who were considered still competent to make an informed decision.
I don't want to die in a morphine-induced haze.