About nine months ago I was re-reading Homer's The Illiad and I noticed something: Armor is mentioned a lot.
Now, you can strap some metal on yourself and call it armor, but these guys didn't do that. This stuff was glittery. And they made it a point to be so. But to what purpose? Why would a giant plume on your head protect you from your enemies? In the Illiad, men would see a hero coming in all of his armor and they would lose heart and run. He was invincible to them. And he practically was. Armor often saved the lives of the hero on the plains before Troy.
I read in R. Scott Bakker's Prince of Nothing Trilogy that a battle is just an argument to convince your foe that he will lose. You don't need to kill the entire army....you just need to make them run away. Sun Tzu pretty much said the same thing: "Hence to fight and conquer in all your battles is not supreme excellence; supreme excellence consists in breaking the enemy's resistance without fighting."
Equally important to convincing your foe that he will lose, is convincing yourself that you will win. Being encased in metal not only protects you, it makes you feel protected. It helps to take your mind off of defense and focus on offense.
Lastly, armor attracts attention. In a military sense, very unwanted attention. Likewise, the more points a male deer has the more of a prize he becomes for hunters. But at the same time it's yet another declaration of invincibility. You can attract dangerous attention and you can handle it.
When we wear our finest, and look our best, we convey all of this information in less then a second to anyone who looks in our direction.