I guess you haven't walked up to a cash register with cash in hand lately then.
Take rolls of pennies, or nickels with you and see how the store owner likes your cash. Was a time store owners would gladly take US currency here, but now it's not worth losing money on, waiting for it to get past par, which looks doubtful.
Ever see the look on a clerk's face when they have to make change? Cash is passe in real worth, it's coming down to human value now.