I don't really want to get into this discussion, but I do mostly agree with Goldfinch. We have a lot to do in the area of end of life decision making/care. But, in the end, one may never know how you will feel. My mom had a DNR/living will, but in the end, every time my brother asked her if she wanted to keep going during her last crisis after a liver transplant, her answer was yes. She was 67 and she emphatically was not ready to die. Of course, when the last thing didn't work, my dad and brother made that decision for her.
And, yes, like Oak states, we wouldn't have to deal with a lot of these decisions, if we actually did preventative care. But, that extends to the consumers, too, not just medical professionals (disclaimer, I am one of them, though thankfully, not a doctor!). Many people just don't take responsibility for their health, even when they have insurance. We all know how hard it is to get people to exercise and eat healthily. I don't want to go off on that tangent, but at a certain level, if people refuse to use the things that we know will work to avoid actually getting diseases like diabetes in the first place, then I am not sure what we can do. This is an area that really interests me, because so many people have distortions about health, fitness, and just being overall well in mind and body. I see it every day in my work, even though I am dealing with mental health. For example, it's quite difficult for me to get people to actually use/practice things like breathing, visualization, muscle relaxation, or exercise that are proven empirically to reduce anxiety and depression. I tell them I am writing them a "prescription," just like the doctor who gives them medication, but this comes with no side effects. Let's just say, it's very hard to get this point across, even with people who are well educated. My own friends would rather take a pill.
I would never refuse treatment for anything, unless I was told I had like two days to live. However, I wouldn't be heroic, either, after a certain point.

Today is Yom Kippur and I decided to repent for my sins by going on a bike ride . I needed some space; I had to hospitalize a 6 year old last week and I have two teenagers who are suicidal/in crisis. I decided to make it a destination ride, but I did an 11 mile loop, then I went to Trader Joe's where I had a trauma, because they moved the nuts and cranberries! So, I rode 15.5 miles, I feel better and now I can relax.