This doesn't compare apples to apples, as the issue isn't really about operating systems but more about platforms and integration philosophy: on Windows, the people who make the graphics hardware are able to build drivers for their hardware that support OpenGL, Vulkan, etc.. On macOS, one of two things happens, depending on the device: either 1) Apple does most of the work to create the graphics hardware, and then refuses to support anything designed by Khronos; or 2) Apple buys most of the graphics hardware from a third party, but doesn't really offer a way for third-parties to develop kernel modules / drivers with the depth of access required to pull off a useful graphics driver. "Part of me wonders if NVIDIA was writing the OpenGL for Apple" <- FWIW, I went to college with two of the people who worked--at Apple--on their OpenGL stack: it wasn't third-party.