Are we talking about concept, or are we talking about how majority of people implement it? Anyway, I know a game that has adequate explanation, albeit through a gameplay.
I have to repeat my question. Because otherwise, we are comparing examples, which will lead us to nowhere. You will keep mentioning this simple sword that is completely impractical and unusuable, and say how this is the same as bikini armor, it has the same logic. Both are impractical and unusuable.
And I will simply reply with, are we talking about fantasy, or not? Are we talking about piece of metal and a piece of leather? Or are we talking about a magical artifact that draws magical force of the user through his blood, and gains double the length while weighting like a shortsword, less than kilo. The magic bloodblade is able to slice through stone troll's skin like hot knife through butter. And a small leather waisband made out of some fantasy creature that allows magic to flow better. Are we talking about real life objects, or fantasy artifacts?