Stablesats pay a 0% annual return whereas stablecoins and money market accounts pay a 5% annual return (granted, stablecoins only do that when you keep them in a contract like uniswap, but they still do it). Stablesats are simply not as good as their competition because they do not pay you anything. Stablesats are the worst part of cash: a terrible place to store money. But they are even worse because they don't inherit the best part of cash, which is wide acceptance. So you are left with a not-widely-accepted medium of exchange that doesn't even reward you for holding it. Few people want that.