Wedding rings are worn on the left hand's ring finger because it has a vein inside it that is supposedly connected to the heart.. I know it's not an actual fact about the heart but I thought it would be quite interesting, sorry if this doesn't actually help =p

Well it's probably because generally people trust statistics and facts, because they immediately assume that it has professionally been proven and so therefore they should trust it. But yes, it is psychological people automatically tend to side with facts or other people's opinions when they match their own.