That's Pixar - they're behind the curve, and PRMan 17 and 18 (their commercial renderer they sell) has been pretty poor at full raytracing (monte-carlo integration) due to poor acceleration structures and the overhead of their RSL shading language.
PRMan 19 looks like it's going to fix these issues to some degree.
Other renderers like Arnold and VRay (full raytracers) have been being used for the last 5 years by other studios.
