And sure, I think most people would argue it's not worth spending another $500,000 treating a terminally ill patient with a 0% chance of survival.
But often the chance isn't 0%, it might be 15%. So if it's your loved one who has stage 4 cancer and the doctor says "it's going to cost a lot of money and only a 15% chance we'll cure the cancer", not many people will say "meh... those odds aren't good enough, so lets just put grandpa in a hospice and let him go"