Look at what they presented. Sure, they streamed it online and made it flashy for everyone to use, because they know such a reveal to game devs would've been leaked anyways. But the presentation clearly missed stuff consumers would be interested (pricing, game lineup), while it contained everything game devs are interested. Not only contained, they put time into each detail how the service can help game developers realize their game vision.
They also showed how the consumer/ gamer benefits from the features as well.
They didn't show off other stuff because they can always have a 2nd presentation to do that. Its an easy way to sustain interest (especially if this presentation didn't have the positive impact Google was hoping for) and just part of the general marketing cycle. After all, Sony also used 2 presentations to give out all the necessary PS4 info consumers required.