That conversation can hurt. Which is exactly why people avoid it. But that doesn't change the inevitable. A smaller amount of pain now can save larger amounts of pain in the future. It is the best approach, even though it is difficult.

The thing about whether it's in writing or not is that unless it IS in writing, medical personnel are legally bound to act as if there ARE no wishes in place. All available measures. Then it's all down the rabbit hole.

All I can say about understanding them is this: They are doing the responsible thing. Many, many do not. They are likely trying to save you as much pain as possible. You are very lucky that way.