The major unknown that prevented this until now was the average age of the people working at the FAA. For a long time any request for something unusual was met with the simple response, "No". The FAA's mandate is safety, and they could justify disallowing new things for the sake of safety. They've finally realized that this is inevitable, and they can't just say "No" forever. A lot of the old guard is retiring, and the newer employees are figuring out how to integrate new technology safely.