As a Swede living in the US, the difference is in Sweden the SSN is your username, in the US it's become the password.
(They remember it, or they write it down and store it with their other valuable pieces of paper.)
In practice, by just marking the damn pages.
Edit: latest statistics show >95% have BankId on a smartphone. See https://www.bankid.com/assets/bankid/stats/2019/statistik-20...