Most justice systems are built on the assumption that it's better to let 100 guilty people go than convicting one innocent person. Once we accept that it's OK to convict innocent people as long as the averages are fine then we are heading into serious trouble.
You're comparing a merchant system with a criminal justice system. Obviously the cost or the downside of false positive is very different between those two, as well as the cost of making the judgement itself, given the difference in scale.
