The sound you are hearing is the rattling of armor plates, not the clink of metal on ground. While leg armor generally has more leather and padding between plates, body armor is more designed from the top and let gravity hold it all down, and doesn't need much padding since it's a more static piece of armor. If you look at it that way, upper body makes more sense. Even chain leggings need to be bound with other materials and made taught, so they don't make as much sound as you would think. Some of this information is from experience mind you..... pauldrons REALLY start to get on your nerve when the clinking is beside your ear all day.