Optimization is not an on/off switch. All companies are optimising their implementation to the best of their ability/budget. As coders get more familiar with the tech and it becomes more commonplace, as well as work being done by graphics card companies on their drivers, it will reduce the computational requirements over time. There's a hell of a lot of work that goes into graphical processing on hardware, software, engine and game levels to make things look better for less computations, it's not just "tell GPU to do simulate every particle from the sun".