Possibly because they are employed on the basis of who they are, and how upper class they are rather than any ability. Although as a PP said, what does a Lady in Waiting do, apart from stand around socialising. Maybe in days gone by they didnt need to know anything, as the only people invited to Buckingham Palace receptions were people like them, but Charles has been having receptions for people who work with charities he supports for decades. He possibly kept his mother's ladies in Waiting at arms length.
I wear name badges a lot. I don't notice it at all once its on! What excuse do you have for her interrogating her as if she was in a police interview?