because on a certain level, it's a huge Ponzi scheme. And the little ones (yep, 50B is a little one) become symbols that bring the Ponzi-nature of the whole system to the consensus consciousness. Which is a really bad thing. I've thought for a long time that's probably what happened to the Maya civilization.
Another little one: what is the dollar but a Ponzi scheme? And even when it was backed by gold, gold itself, while it has some real value, is mostly valuable because you think there will be some other investor out there who will throw their money into the investment. Gold a Ponzi scheme except when it is plating on electronics or jewelry.