A Brief Note on Insurance
An insurance policy is an agreement to turn the possibility of an improbable unaffordable expense into a certain affordable expense. It is not a magic means of making a certain expense affordable.
For example, paying for birth control is highly probable. Needing vaccines or some medical tests is highly probable. Living long enough to retire is highly probable nowadays (although it wasn't back when old-age pensions were invented). An “insurance” policy that pays for such things is, at best, a matter of taking your money for a wild night out on the town and giving some of it back to you.
In other words, an alleged study that shows that lack of health insurance caused some people to forgo colonoscopies, etc. should be regarded with great skepticism. A lack of something might have stopped the colonoscopies/vaccines/birth-control/whatever but that something is not health insurance. It might be correlated with lack of health insurance. It might be lack of good advice or lack of a job.