Must be because there is nothing new to announce, only new itterations ?
It's in the spirit of Channel 9:
"The PDC has always provided direct access to the people behind the technologies, but this year we’re upping the ante by providing access to the places, too. For the first time ever, our most influential customers will converge on the Microsoft Campus
in Redmond for the PDC. We’re opening the doors to our buildings and labs, and providing unprecedented access to Microsoft’s leaders and engineering teams on their home turf."
The price tag will still prevent me from coming though, but it looks promising to me.