Just like Zimbabwe in the good old days of 2008, "updating" prices constantly would have deleterious effects on purchasing by normal people.
When prices in some system have to be updated constantly to reflect another metric (say, USD), it may be more efficient to just use that other metric in the price. This is what happened in Zimbabwe.
Updating them constantly will be bad, yes. But prices don't need to remain perfectly fixed. Prices on Amazon, for example, fluctuate all the time. Most products stay at the same price, but plenty fluctuate a couple percent on a daily basis.