It's not, but the simple fact of the matter is that people won't use inflation bucks and will instead use a medium of exchange that doesn't lose 30% of its value a year. There are modern examples of this very thing going on, and what happens, exactly, is that people and businesses stop accepting the government currency with as payment, and insist on another currency or medium, which results in people not using it (or accepting it for their labor) and puts the government currency into a devaluation death spiral. Within months or years, you see government bank notes for denominations in the millions and billions, and before you know it, Z$100 billion won't even buy you a pack of smokes. (You can now buy mint, never circulated Zimbabwe denomination notes as novelty items. I, for example, am a quadrillionaire, if you count my Zimbabwe dollars, which include bills that have a denomination of 100
trillion.)
Seriously, check out the graph of inflation rates
here.
Granted, a modern country without the same problems as Zimbabwe won't have it as bad, but with sustained, mid/low double digit inflation per annum, total currency abandonment is a certainty, and if you read up on Zimbabwe, you'll see that even before hyper inflation kicked in and people were changing their inflation bucks for something else multiple times a day, most people didn't use the official government currency, and instead sold it on the black market for non-inflating currencies, which functioned as the country's primary medium of exchange.
Yeah, they try, but I'm a hell of lot smarter than the government, so you can guess how complete and accurate a job they actually manage to do with that.