The problem / applications

• prove to a new employer that you really have certain qualifications
• prove to a new bank, when opening an account, that you are who you say you are
• pick up a new prescription from whichever pharmacy you happen to be passing (rather than choosing a pharmacy when at your GP)
• show your health records to a new doctor (or your dental records to a dentist . . .)
• act on behalf of someone else online (akin to a power of attorney), or
• pay face-to-face, and quote a loyalty card number, in a single easy action

and there are many similar applications.