Armor textures are designed to look cool for the most part, not be practical. Armor should be designed to deflect blows ... all the spikes and flanges you see in typical RPG armors would actually catch a blade and focus it. Enormous shoulder pieces would limit mobility of your sword arm, and give your enemy a point of leverage to spin you off target and take you down, to say nothing of what it would do to your peripheral vision. No one in their right mind would make a real armor as fancy as fantasy RPG armors. To say nothing of the fact that every eye on the battlefield would immediately be drawn to the battle-dork with the flashiest armor.
That said, it looks cool, and that is what people expect.
