If things are anything at all like they were when I was at Intel then it is an inability to handle risk. Wafer starts are expensive, masks are expensive, margin

If things are anything at all like they were when I was at Intel then it is an inability to handle risk. Wafer starts are expensive, masks are expensive, margins on this sort of processor are tight. Basically that adds up to nobody wanting to be "that guy" (and it is always a guy) who pushes through the idea that costs the company a few million dollars. As a result, unless some customer both specifically asks for this, and commits to enough volume to insure that they will at least break even, they aren't going to risk it.