People don't pay medical bills all the time. This is literally the space I work in. They can't put your appendix back in.
It is illegal for the hospital to turn you away for emergency services. There is not a lot of incentives to pay big medical bills.
So, what happens? It just drives up costs, in general, because a certain amount of every bill is buffer to make up for everyone else. That's partially why medical in America is crazy expensive.
Pro tip -- never pay what they ask. If you just get the bill and simply ask for them to reduce it, they will gladly knock off at least 10% just for you offering to pay. It's a built in cost.
But yeah, that's what Obamacare was -- it tried to mandate that people had insurance (by offering a tax penalty if you don't) and the flip-side is that insurance companies weren't allowed to deny you for having pre-existing conditions. Republicans fought the mandate...here we are.
The American medical system is a joke. Great quality, but we all pay way more than we need to and don't end up getting the care we need.
So many insurance companies are a joke as well. My wife was denied a CT scan and asked to pay out of pocket. The out of pocket price was less than her United Healthcare price if she had been approved. The same thing happens with prescriptions. I'm all for free enterprise but it's kind of nuts. It would be nice to see all prices up front.