There's nothing particularly rational about either one, it's about what people want.
Actually, there is, and the same applies to a lot of other subjects, like for example drug prohibition.
There are plenty of different systems and methods that demonstrably do or do not work. It really isn't all that hard to look at them and point that out. There's nothing wrong with deliberately choosing not to use a system that works for reasons of principle, but in that case we could at least be honest and consistent about it.
If a nation or a state chooses to make health insurance optional, based on principles of freedom and individual responsibility, then do it properly. Let the corpses of those who were stupid or irresponsible pile up outside the ER for all to see.
Same thing with drug prohibition. It demonstrably doesn't work, it costs tons of money and there's a remarkable correlation between wanting to forbid it and believing in invisible men in the sky, so let's at least have some *honest* reasons why it should be disallowed.