That's not really what's happening at all. It's often cheaper to get an early diagnosis or catch a condition before it progresses too far.
The government doesn't actually hide information about diagnosing or treating diseases, even rare or expensive ones. They do, however, take into account the relative risk of false positives and resulting unnecessary treatments, which often outweigh any benefit of proactive testing for rare diseases.
It's counterintuitive, but if you have a 99% accurate test for something that means you're going to end up with 1 in 100 people getting false positives and undergoing potentially expensive (out of pocket) or dangerous diagnostics and treatments. When considering rare conditions that might only occur in 1 out of 100,000 patients each year, a 99% accurate test results in 1000 unnecessary false positives just to catch the 1 true positive. At scale, this can produce a lot of problems that can actually make life worse on average for the population rather than better.
I agree that there are valid statistical reasons to limit testing, but governments ration care and allow for long wait times when they are responsible for paying the costs. Faster testing and treatment is generally believed to be one of the best things you can do to improve patient outcomes, and government healthcare systems are notoriously bad at this (even worse than private healthcare).
Long wait times don't reduce the rate of false-positives, and false diagnoses. Long wait times deter people from seeking treatment, thus reducing costs.
