> How do you justify the healthy paying for the unhealthy?

Over the course of time, everyone falls into both categories; this idea that there are healthy people is silly, everyone's health fails eventually and often randomly. Healthy is a temporary state. Everyone should contribute so everyone is covered when they become the unhealthy, as they all will.

Better to pay a little bit all of the time than to pay nothing and be unable to afford a giant medical bill that hits you all at once. This is why everyone should pay all of the time, then there's enough money to cover the every changing subset of people, which will eventually include you, who are sick.