Question: Why do they use john doe and jane doe?
Disambiguated questions and answers: question: Why do they use John Doe and Jane Doe instead of the person's real name?
Why do they use John Doe and Jane Doe when talking about someone who isn't real?
answer: true name of a person is unknown or is being intentionally concealed
identity is unknown or unconfirmed
hypothetical "everyman"
Natural Questions answer: refer to an unidentified person (from the Wikipedia article "John Doe")