well of course. they are closed off (in both source and general tribal knowledge. Hell, the docs for GNM/NVN aren't available without a license), locked down to one platform each, and their customer base is overwhelmingly enterprise. And each has a dedicated full time team to consult with. It's no surprise they can give more focused suites when their job is more or less to wrap you into their respective ecosystem.

If you are fine focusing on one platform, or relying on a huge library/framework/engine to abstract all these APIs for you (which remember, you need to provide some license for, except DX12. So another barrier), you can get a bit more convenience. But if you can't use those and/or want to target Linux/Android, you lose some of that for a more flexible, agnostic API (and probably some small performance hitches on the highest end. Vulkan can't assume 2-3 configurations like Gnm/NVN after all).

>if it wasn't for Apple endorsing GL ES on the iPhone, no one would have cared.

Well, Apple at the time basically made people care about mobile graphics at all, so you are technically right. But they could have raised Glide from the dead and made that matter for all the early control they had.

Apple certainly does have a rich history with OpenGL, but we all know how that eventually ended up. It was a long time coming but the breakup was much more spontaneous than I ever would have guessed. Definitely seems to be more than technical shortcomings behind that story.