Of course the effect is subjective and varied, but oftentimes I've found that people that claim a decision being down to appearance to be those that blame their computer when their code doesn't run :)
Perhaps some fields demand this like marketing where certain sorts of marketing are hard to quantify/value objectively so you need to show confidence so that the department keeps its funding!
People who are by their own admission lack confidence will not enter situations where the probability of rejection is high. Confident people will enter a greater number of these situations, and will continue to enter them even if they were rejected previously.