But at the earlier point in time, when people are buying insurance, these are unknown future costs.
And this is the whole problem, insurers don't want to pay those costs because that would increase the premiums they need to charge, making them uncompetitive (and then you're into the realm of behavioural economics), but what people actually want is something that can insure against spending on chronic diseases, which accounts for 90% of the spending on healthcare in the US.
And IMO, to the extent that insurance doesn't cover chronic conditions, it is a bad model for healthcare.