Apple aggressively pushed openCL when it was new, and NVIDIA and AMD aggressively pushed their platform specific CUDA APIs, so all anyone did was complain about

Apple aggressively pushed openCL when it was new, and NVIDIA and AMD aggressively pushed their platform specific CUDA APIs, so all anyone did was complain about apple using openCL when no vendors supported it. Apple had (runtime and ABI) stable openCL built into macOS and iOS by default and on desktop devs kept requiring you install NVIDIAs or AMDs CUDA systems, and on iOS everyone found that openCL was just as clunky to use as openGL. Apple made proprietary APIs that were more usable and better interacted with the hardware, and everyone just used those instead, until Apple deprecated openCL and openGL as they merely represent a pile of engineering work and support that is essentially unused.