Progressives, with their faith in technocracy, are often content with the idea that experts can, across a large system, make reasonable calculations about such things. If a 85-year-old has a 20% chance of benefittig from a liver transplant, then give the new liver to someone else, etc. Is it better to have a system like the one we currently have, where there is some chance involved? In that chance, there is, I suspect, more room for individuals to make measured calculations of risk and reward for themselves. There is also less blunt discussion of when it is time for our parents, grandparents, etc., to stop fighting for life. I'm not sure I want to live in a society where such decisions are made by a rule, created by expert ethicists (partly because I don't think that people with PhDs in ethics are, in fact, better at making such rules). But if there is a single payer for health care, there must be such rules. How else can the government make such decisions?
To reiterate a favorite point, the US is not a small republc. In a republic of a few thousand, it might be possible to have a real, and legitimate community consensus about such things, and also to allow some play in the system. In a large republic, of thousands of communities, that's simply not possible. People get reduced to atoms in a health care system that coveres a republic of 300 million.