I think it has more to do with getting uptake among the WCF crowd than anything else. IF MS doesn't specifically call it out the folks that had bought into the kool-aid to use WCF for all services probably would never see it. As it is, only 50% of them will see it.
The MS stack has a LOT of 80% developers who are buried in the bowels of some organization happily doing the same thing they've been doing since they first learned .NET.
Heck, I had a call from an organization the other day looking for a senior developer, but they had to have intimate knowledge of a perticular third parties UI control library, because that was what they were using when they wrote the original application in VB6. Couldn't convince them that they probably don't need the 3rd party controls for an HTML app, not could I convince them that any senior developer worth hiring would be able to understand and use said library in a matter of hours if they were truly needed.
Over the last three years I've come to understand that it's I'm not that I'm awesome, it's that most developers are just bad at their jobs (present company probably excluded).