The primary advantage of this pattern is it allows you to use different authentication mechanisms on a per-user basis. For example, for convenience, you may wa

The primary advantage of this pattern is it allows you to use different authentication mechanisms on a per-user basis. For example, for convenience, you may want to allow some users to sign in with a single non-password factor, like a FaceID/TouchID/Security Key. But you still want to let users with a password continue signing in with a password, since you don't want to break login for all of your customers at once.