How would you know that they are who they claim to be?

There is an urban legend in my city that a person claiming to be a parking attendant worked outside the zoo for 20 years, pretending to work for either the local government or the zoo, collecting parking fees from visitors.

https://www.snopes.com/fact-check/fake-parking-attendant/

This is, of course, false - but there is no practical way for regular people to verify that people in a public place are who they claim to be.