You’re blaming it on lack preventative care, but the truth is that there is very little preventative care that is shown to be effective at anything more than burning money. The few things that are effective (e.g. vaccines) are largely inexpensive, and don’t require “insurance” as we know it.
Most of the things that are predictable and lead to long-term bad outcomes are behavioral (i.e. diet and exercise; smoking cessation; quitting drugs), and therefore both largely unaffected by medical care, and heavily confounded with socioeconomic status. Your doctor cannot make you eat better and exercise and quit smoking.
In the developed world, if you don’t die at birth or succumb to diseases of lifestyle (diabetes, heart disease, addiction) or accidents, you basically then die of cancer. The lifestyle diseases cannot be prevented by a doctor, and we have essentially no ability to prevent cancer. It’s all just acute treatment.
North Americans in particular hate to hear this, because they have an almost religious faith in doctors based on decades of bad TV. Honestly, though, doctors are pretty impotent when it comes to prevention of illness, and it is ironically this desire for treatment that is helping to balloon costs.