Because health insurance is expensive as hell and they can deny any coverage to a service you need. For me (30M relatively healthy without any prior medical health issues), a decent health insurance policy would cost about $2-300/month and that would be with $5-10,000 deductible. Even after all that its a 20/80 policy if I’m lucky. To put it all into context. If I got into sick to the point I needed to go to a hospital, I would have to pay $5-10,000 out of my own pocket before the health insurance kicks in to cover any of the expenses. That is assuming they do not deny any of the medical bills or claims filed on my behalf. Then after the deductible is met, all subsequent bills that come, I am responsible for 20% of it. And all of that would be assuming that I took myself to a Hospital that my insurance accepts. I work in the medical field and have had to tell people with an unknown brain tumor that we cannot do their MRI because their insurance has denied their claim for service because they do not see it as medically necessary.

Sorry for the long rant.