> Why are the rates of over-testing and over-diagnosis so high?
It is something health systems are aware of and working on, but if you go to the doctor with lower back pain and they say, get a better pair of shoes, take epsom salt baths, and deal with it, you might get frustrated. It doesn't cost the physician anything to order an MRI, but that procedure alone can costs $10k to your insurance, and may very well not reveal anything novel from the physical. But both the patient and physician feel more confident and there is no incentive against the physician for ordering the test. This particular example is such an issue, that a national quality measurement standards org has a measure dedicated to it:
https://www.ncqa.org/hedis/measures/use-of-imaging-studies-f...
And now that we are monitoring it (at some cases, down to the physician level), we can see awareness grow and individual physicians are changing their ordering habits. Very cool.
