No offense but..why would valve purposely hide the real numbers?
Shouldn't it be good news for the PC gaming industry developers and everyone else to know that DD is the future for pc gaming?
...Its because most distributors can't.
Sales data are protected by NDAs between the publisher, the platform, and the distributor. Therefore, Valve would have to break over 200 NDA's signed by the various publishers in order to give out any sort of sales data. The individual publishers/developers can, and sometimes do, but if Valve does it, it would invite lawsuits that Valve doesn't need.
Back from the dead, I'm afraid.