Biden's ego has made it impossible for him to understand the uses he has been put to. And that is part of the joke. Joe Biden wasn't selected despite his penchant for saying stupid things in public. He was selected because of it. He is there to project incompetence in order to make Obama look better. He is there to make the idea of white male leadership look like a joke. That is his one and only job and he has succeeded at it.
Biden is the successor of every dumb white male father figure on TV gawping at the screen, tumbling over chairs and down the stairs, scratching his head cluelessly at the wiser new generation around him. He is every man in a commercial who can't figure out how to start a car, make coffee or clean the house until his wife or a helpful minority figure shows up and explains it to him.