Just because it sounds cool -- Look it up!

[Areala-chan]

To be fair, bra makers collectively don't seem to know either.

Most womens' clothing manufacturers don't adhere to standardized sizing, which is why, yes, we really do have to try on EVERY pair of jeans even though they all say they're the same size. Sometimes a 4 is really a 6, a Small is really a Medium, and god help you if your waist, bust, or hips measure in at an odd number of inches.

 

[THBGato]

And why do so few dresses (and even trousers sometimes) not have pockets! Grrrr!