[TazeTSchnitzel]

OpenGL compute shaders are a natural step if you have unified programmable shader cores, and less complicated than adding new pipeline stages for everything (tessellation shaders, geometry shaders, …).

Khronos could have chosen only to add OpenCL integration, but OpenCL C is a very different language to GLSL, the memory model (among other things) is different, and so on. I don't see why video game developers should be forced to use OpenCL when they want to work with the outputs of OpenGL rendering passes, to produce inputs to OpenGL rendering passes, scheduled in OpenGL, to do things that don't fit neatly into vertex or fragment shaders?