>If there were no limits on health insurance there would be little backpressure to ensure that care provided is worth paying for, or to put it another way, has real benefit.

And yet the US has a severe problem with over-diagnosis and over-treatment of a wide range of stuff, causing a lot of harm to many people. This overtreatment has driven up costs; it's one of the reasons medical costs in the US are so high.

https://en.wikipedia.org/wiki/Unnecessary_health_care