I think when people check themselves out in the mirror, it is usually ultimately with the intent of verifying that the way they look is sending the signal that they want other people to receive.

It's kind of akin to an author proofreading an article that they've written. Although an author may read and re-read their own article several times prior to publishing, the author is ultimately writing the article to send a message to other people, not to themselves.

Does that make sense?