They did, it's called Ripple! LMAO that coin has huge potential to be a capital sponge that absorbs inflation and acts like a pressure release valve for the market or balance sheet of their choice! It's freaking diabolically genius since the vast majority of tokens are held by the "house" so they can manipulate supply and therefore price. It's like a big knob they can turn to create or destroy capital without consequence. Incredible.