Honestly? I don't think this is true anymore. :/
I think what we're seeing here is that all 3 major companies are content to release new information at their own pace, whether via magazine/online reveals or with their own dedicated events. All in all, it seems the impact of E3 in generating hype for unannounced games is slowly getting marginalized, or at least being redirected to a more mainstream audience. The main centerpieces of the three major conferences that were previously unannounced are, respectively, Smartglass, Wonderbook, and Nintendoland. That tells us all we need to know.
It's a strange disconnect I'm seeing, because people are legitimately angry that nothing new was shown, but standing back and looking, what we DO know about each console and their games is still pretty damn good in the short term. Yes, including Vita and Wii U.
Is this actually a problem with their approach, or is it a problem with our expectations?