One of the comments said

You can expect this to continue happening for as long as Apple pushes Metal and refuses to support Vulkan [...] If macOS wants to get anywhere it has to be a case "why not support it" instead of "we need to make a Metal compatible version of our engine".

And I couldn't have said it better myself

Don't forget that Apple actively breaks software build processes quite frequently for their platform and doesn't allow you to fully automate a lot of them because you need accounts to download the relevant tools and can only use them on Apple hardware. That makes supporting it a pain for cross platform projects.