You’re right that usernames are an ID, the password allows the system to authenticate you are who you say you are (but it’s easily exploited). There’s no reaso

You’re right that usernames are an ID, the password allows the system to authenticate you are who you say you are (but it’s easily exploited). There’s no reason why biometrics can’t both Id and authn at the same time, as long as both functions have a high degree of confidence. Multi factor auth is probably always going to have its place. Where the confidence level is low in the authn, it must be increased by adding additional vectors.