Why doesn't MS just kill the Xbox and launch a certification program?

I've been wondering the reasons for the existence of the Xbox hardware, given the unstoppable decline that the console industry is going through. As far as I know, Microsoft does not really earn significant amounts of money from the Xbox and that may not change with the Xbox 720 as high end graphics are still expensive. I understand that there is a "battle for the living room" but that battle can be fought with an inexpensive set top box device instead, as long as the services are there. Do you guys think the next wave of consoles would reignite the console business? as attention is been brought to the PC, a hardware certification program may even give desktop computers a reason for existence other than heavy compute workloads and the traditional PC gaming experience. I think that this may even be the plan at the end of the day due to the rebranding that Xbox is receiving, it is not a console anymore, it is a set of top of the line entertainment services. That will certainly cause a stroke to Mr. Newell. Now, before people start quietly yelling, I'm aware of the advantages that a dedicated gaming machine offers in terms of performance and optimization, It is just that most AAA games are also available on the PC anyways.