Generally, 'light armor' implies that it's the most agile and non-constricting while offering a minimal amount of ballistic/energy protection. In pirate terms, it can also mean that the pieces have been pulled off of corpses, since they're dead, the armor isn't really that good now is it. Chest-pieces will have bullet-holes that killed their previous owner. Shoulder pads will have cracked shells, seriously diminishing the protective value.