Well, it's more a matter of how consumer-level 3D hardware is optimized. 3D games use triangles, so the hardware is designed to handle triangles only. Poser meshes are typically built with quads. So for the geometry to work with a GeForce4, for instance, you'd need to convert it to triangles first. For now, this conversion would have to be done with the CPU, so any performance gains would be offset. But a few years down the road, who knows?