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Probably because there aren't all that many options. When there are alternative options, people will probably use them.
This is from a comment on the article:
John, people do abandon hyperinflated currency very quickly and turn to hard currencies, like US dollar or gold, the only problem is that in most cases it is prohibited by the local law… I learned it hard way back in 1970/80s in Poland then ruled by communists and burdened by inflation of 100%/month: everybody used dollars (at least for larger purchases) risking bars.