If the early Project Stream test is anything to go by, Google's goal is simple: it wants to make a streaming service that offers top-tier games across a bevy of devices, including Chromecast dongles and (according to Kotaku) dedicated hardware. An appearance at GDC would make sense in that light. Google would need to encourage developers to sign up for the service and (if necessary) optimize their titles, and it would have few better opportunities than a conference where it can network with studios and offer technical expertise.