On his blog, JP Koning argues that very short conversion periods rendered it unattractive for Swedes to hold cash. He also suggests that it were the banks that pushed for the short periods.
While digital payments share some of the blame for the obsolescence of paper kronor, the Riksbank is also responsible. The Riksbank betrayed the Swedish cash-using public this decade by embarking on an aggressive note switch. Had it chosen a more customer friendly approach, Swedes would be holding a much larger stock of banknotes than they are now. As long as other countries don’t enact the same policies as Sweden, they needn’t worry about precipitous declines in cash demand.
Recently, the trend decline of kronor cash holdings has reverted. Across the board, the use case for cash seems to change (see also this post).
… even as developed countries are seeing fewer transactions completed using cash, the quantity of banknotes outstanding has jumped. This increase in cash outstanding, which generally exceeds GDP growth, is mostly due to an increase in demand for large-value denominations, as the chart below illustrates: