That's because, in a blunt sense, no one cares about the Argentinian peso except for (some) Argentinians. Many more people (practically everyone) care about the USD. So long as the US commands dominant global influence (in many senses) then the USD retains a "standard" quality that can be very flexible. Sustained deflation and loss of purchase power is far more dangerous than inflation, so long as you don't slip into hyperinflation. Everyone in Argentina, for instance, just immediately converted their money to USD.