Why are things that you wear on the bottom half of you plural?  Pants, pantaloons, panties, bloomers, boxers, briefs, culottes, tights, jeans, shorts, slacks.  For socks and sock-like things it makes sense because there are two individual objects, but a pair of pants?  Is each pant leg a “pant?”  Why don’t I call each sleeve of my shirt a “shirt” and the whole thing a “pair of shirts?”

Why is a loincloth, on the other hand, singular?