My grandma always told me when she couldn’t go on her walks anymore she didn’t consider life worth living. When she got dementia she was placed in a closed hospice, to “protect her”. Now she only walks when I visit, and I only see a shell of the woman she was. Anecdotal of course, but why do people think it’s an ethics question when society is individualistic as can be? There is no choice in being born, why don’t we…
To my mind the main obstacle is kind of orthogonal: how do you protect the people who don't want to go, being pressured or manipulated. I agree that if someone is really, independently and committedly deciding to go, you shouldn't stop them. But how do you express that test in a bureaucratic, legalistic framework? In a friend's family, there was a big rift as one family member in direct line of inheritance was accuse…
This is why it's important to have a pretty detailed living will[1]. Especially is you're already chronically ill and have a pretty good idea of how that road ends.
[1] https://en.wikipedia.org/wiki/Advance_healthcare_directive