AZShooter and Ryan,
Those are great examples of how well the .300WSM shoots. Which just goes to show that its lack of general acceptance by the long range crowd is all the more baffling.
Perhaps the problem is that when people think ".300WSM," they automatically think "short action," which hampers shooting the long heavy bullets favored by the long range people, and thus they quickly move on to other cartridges for consideration.
Also, maybe, once there is a lag in a cartridge's popularity, manufacturers scale back brass production, then people start to feel like brass is hard to find, and so people shy away from the cartridge which further reduces demand, which then reduces production even more, and the negative-feedback-loop death-spiral continues downward.
I have no special knowledge, I am just throwing out possibilities.