Doctors generate better knowledge of efficacy than of risk, and this skews decisionmaking,” he says. “They design treatments to do something specific, and design studies to see if those treatments achieved those outcomes; and so accumulate lots of data on whether treatments produce the desired effects. Capturing good knowledge of side effects, especially the unanticipated ones that are so common, is both less interesting and more difficult. Whenever doctors have more thorough knowledge of the possible benefits of a treatment than they do of its potential risks, patients and doctors will lean towards intervention.
David S. Jones via The passion for procedures to fix ailing arteries and hearts may be misguided - Alice Park

I’m convinced that this bias is responsible for a very large portion of surgical intervention. My wife is, coincidentally, planning a study on the overuse of angioplasty.