Actually, thats what it is secured by, which is terrible but different. What it’s backed by (exchangeable for) is debt obligations.

The gold standard was also enforced by men with guns. But you and I and our mortgages have replaced gold. We are the reserve asset. 

 True. True. 
It’s why Bitcoin is programmed to go up forever.   That’s how it’s supposed to be with a true (non slave) reserve asset.