One of the biggest challenges of being an auto-didact is proving that you know the material. For instance, if you are a self-taught programmer without a formal degree, it's hard to prove that you know as much as someone who has a degree without a previous stellar job history. The degree is a seal of quality on a person.

It would be cool if elite institutions offered a way for people to certify themselves using their stringent criteria without having to pay, or spend the time, for the full course. They would obviously never do that as they would lose a lot of money - assuming this idea is even possible in practice.