I don't know, feels like a massive waste of resources and if Google is doing it simply because it can. It's probably much cheaper for everyone else to handle latency/throughput problems on the client side and application level, sticking to all the traditional networking, but not relying on it for quality. Even in the web browser we already can send all kinds of asynchronous requests to multiple servers in multiple datacenters, choosing the fastest response and making all kinds of decisions to where to send requests dynamically in real time.
And while I agree about overcomplicated routers and box-centric thinking in computer networks, it's pretty much impossible to change things because of the monopolistic nature of the ISP industry. They are very far from competing on the levels of quality where SDN could matter.