The difficult thing with hiring bad candidates vs not hiring bad candidates is that you get to experience the bad hire every single day, so it is quite apparent that you made a mistake. With not hiring a good candidate, you don't really know what you were missing. You may just assume that the best applicant you reject is no better than your average employee. But there is a chance that that person would bring something to the table so unexpected that you can't even imagine the world that would have been had you hired them.