Because that would be admitting there is a problem. Do you want to be the politician that authorizes change in denomination while simultaneously explaining why you haven't addressed why that is required. I'm guessing the politicians don't want to touch inflation with a 10 foot pole, because solving inflation is painful in the beginning so it tends to be very bad for anyone elected on any timespan less than a decade.

Milton Friedman called inflation like alcoholism, great at the start but quitting is long and painful and most of the rewards of stopping are delayed with only pain up front.