I sort of disagree that healthcare is about the nation; it's about people as individuals.

If you weren't an officer of a biomedical company I wish to do well I'd let you continue down your merry libertarian path. As it is, if my taxes are in any way paying for your health, your health is an aspect of my social contract. The private sector is best at internalizing profit and externalizing loss and in a system as closed as a nation's citizenry that externality only leaves the private sector, not the system as a whole. Absolutely: walking is good medicine. but considering there's no profit motive to make people walk, it comes down to individual initiative. Meanwhile, there's a deep and wide profit motive to make people take an Uber, so in effect we're allowing internalized profit motives to damage externalized public health.

If healthcare were about the nation, we'd outlaw smoking and make exercise mandatory, but then we'd be living in a place that none of us wants to live in.

We tax the shit out of it and require exercise of children, all the while doing our goddamnedest to instill healthy habits. This isn't an either/or problem, it's an optimizing problem and part of that optimization is recognizing that even if Cletus the slack-jawed couch potato doesn't want to walk to work, his poor health costs me tax dollars so fuckin' hell let's socialize whatever we can to optimize his health for the betterment of all our budgets.