Being terminally ill isn’t living I understand their reasoning the sting of death shouldn’t be a drawn out ordeal seen to many family go that way.
I cannot find a single example in the Bible of a righteous man or woman taking his/her own life, even those with presumable cause to do so (e.g. King David suffered from poor circulation and was cold all the time; the prophet Elisha died of an illness).
Oh of course, just “put them to sleep” like an old dog or horse with broken leg.
Hell, many peoples’ entire lives are a long drawn out ordeal. I guess a lot of people just need killing; of course for their own good....