Although they created and gave OpenCL 1.0 to Khronos, they were not happy with the path that Khronos was taking it and their support basically stagnated on OpenCL 1.0.
As side note Google is yet to support OpenCL on Android, instead just like they did with their Android Java, they decided to create their own flavour, Renderscript, which isn't compatible with OpenCL.
As for OpenGL ES, I bet they only did it, as they were trying to "play pretend" being another kind of Apple as survival mechanism, nowadays they don't need it any longer.
Finally, Metal is one year older than Vulkan, offers a modern API instead of plain old C, and contrary to Khronos, just like other platform vendors, Apple understands the value of providing nice frameworks and debugging tools to go along an API.