I said 'some people' would be relieved, not that I would be. My father-in-law had throat cancer, and he was in a ton of pain, actively wishing to get it over with. This was way before the time of legalized euthanasia in Canada. My MIL was relieved when he passed. Mom had Alzheimer's, we were all relieved (and sad) when she finally passed. Again, before the time of legalized euthanasia.
I have been depressed, but not like the cases being discussed here. But I don't feel I can judge that person. I've seen some long term depression as well. One younger person, a friend of my daughters, had copper poisoning, a painful condition where he could not digest copper, and it built up in his system. It was depressing to him. So much that he needed constant watching, as he was actively trying to end the pain by jumping out windows, swallowing excessive drugs, pulling out his IVs and such. No known cure for his condition AND it was going to last a long time. A counsellor suggested an alternative, several meetings with several doctors and relatives later, and he willingly put himself out of the pain.
I just don't see things like this in black/white terms. Unless I've walked in those shoes, I reserve judgement.
In Hinduism we have a method ... fasting to death, under medical supervision, with community approval. That's where I personally stand on it. And that's what I would do, which amounts to refusal of food in that circumstance.
I also think certain habits for some people are passive suicide ... smoking, drinking, drug addiction. It's complicated.