Private entities contract with Medicare to provide insurance that covers what Medicare covers (and perhaps more). Would said insurers cover everyone that Medicare covers in the absence of Medicare? The answer is no.
How many of these people on private Medicare plans pay for Medigap? Everyone who get kicked off a private plan can go back to the original Medicare. Your point is disingenuous. Medicare is the universal insurer of last resort for elderly. Their lives would be much worse without this last resort insurer.
> Medicare is the universal insurer of last resort for elderly. Their lives would be much worse without this last resort insurer
That's a far cry from "people don't seek to leave Medicare", which is literally the original claim. By and large, people do seek to leave it, to the extent that they can, both legally and financially.
Yes, for people who can't access anything better, having Medicare is better than literally nothing, but nobody's arguing that. That doesn't mean that Medicare provides a good model of what would best suit everyone else, and that's the relevant question when talking about a single-payer system.
If you want to talk about a single-payer system and use Medicare as an example in support of it, you have to address the fact that privately managed plans consistently outperform Medicare on the top three performance indicators, and that patients themselves prefer all the alternatives to Medicare except "no coverage at all".
How many of these people on private Medicare plans pay for Medigap? Everyone who get kicked off a private plan can go back to the original Medicare. Your point is disingenuous. Medicare is the universal insurer of last resort for elderly. Their lives would be much worse without this last resort insurer.