Herein lies a major problem with our health care system: Its hard to put the genie back in the bottle. It shouldn't be! I have no doubt that there are tons of things that physicians do to patients, expensive things that have never been rigorously studied, that actually hurt patients more than help. Very few physicians have the courage (or the funding) to look for them.
To be fair, docs aren't the only cause of this problem. I am not sure we are completely protected (legally) if we want to carry out some of these studies. Also in America we have a very demanding culture of consumption. People always want their doctors to "do something!" to fix their ailments. A classic example are patients with viral infections who insist on antibiotics. The physicians finally just get sick of hearing about it, stop fighting, and write the script. And now we have antibiotic resistance.
If we can't even talk patients out of antibiotics for a cold, are we going to be able convince them to forego a surgery or some other major treatment that has been standard of care for decades for the sake of proving that it actually helps?