There is a difference between being shamed for breaking the build because you didn't run the test suite (and well knew that you should run the test suite) and being shamed for making an innocent mistake because you didn't know better.
Is there really an over-utilization of blood tests? MRIs, yes, but I'm not sure that right now we're really doing too many blood tests.
Regarding your point on Bayes Theorem, that's valid in some ways and invalid in some ways. Suppose someone gets a vitamin D test back at 8 ng/mL. There's not really a chance of a false positive. He's deficient and needs supplementation. Making the test cheaper, faster, and more accessible can really only improve the health of the population. It will likely also drive down the cost of healthcare overall, because vitamin D deficiency has all sorts of unpleasant effects.
Furthermore, the literature suggests that the vast majority of doctors do not understand Bayes Theorem. Source: http://yudkowsky.net/rational/bayes
You are demonstrably wrong about the vitamin d. What if it was a specimen swap, and the lab screwed up and tested someone else's blood instead of yours? This happens.
I think part of it is desperation. If someone is diagnosed with an incurable or untreatable disease or condition, then it's natural to try to look for some sort of treatment that will yield better results.
That means applying less skepticism towards "alternative" therapies.
Then you also have the following working against science:
- Confirmation bias
- Mistaking coincidence with causation
- Overly aggressive pattern matching