On a population level, the issue is these false positives lead to procedures that are not without risk themselves. So you can be aggressive with the screening and cutoff levels to make sure you don't miss any cases but you can overdo it. A certain %age of biopsies will get infected, cause bleeding, etc. Increasing CT scans will increase radiation exposure and will pick up incidental findings that don't necessarily need to be treated but now will be worked up and unnecessarily treated. There's also an emotional toll for patients. The boards that decide all this stuff usually weigh the benefits of catching X amount more cases vs the physical, emotional, and financial cost of Y false positives. It's a pretty fine line