You raise an interesting question, and it does seem there is a purpose for them even if nobody actually uses them. From the Wiki: en.wikipedia.org/…/Banknotes_of_the_Swiss_franc “Switzerland is unusual among affluent countries in that it used to expire its banknotes; the Swiss National Bank has declared several older series of banknotes to be no longer legal tender some time after introducing newer series.[2] Notes from these “recalled” series could be exchanged for still-valid notes at the National Bank for up to 20 years after the date of recall, after which the notes lost all value. When recalled series become valueless, the National Bank transfers an amount of money equal to the sum of the now-worthless notes to a state-run last-resort disaster insurance fund, the Swiss Fund for Aid in Cases of Uninsurable Damage by Natural Forces.[3] In June 2019, the Swiss parliament passed a bill that removed the twenty-year time limit. Effective 1 January 2020, all banknotes starting from the sixth series issued in 1976 as well as any future series remain valid and can be exchanged for current notes indefinitely.[2][3][4][5] In April 2021, the Swiss National Bank announced that it was recalling its eighth series of banknotes issued between 1995 and 1998; the series was replaced by the ninth series launched between 2016 and 2019.[6] In May 2021, the old banknotes lost their status as legal tender and are no longer valid for payments.[6]”