Vulkan is on Android, Direct X is on Windows, Metal is on macOS and iOS.
I don't see anything wrong with it. Just like Windows did't adopt Vulkan. And that is assuming Vulkan is good in the first place.
And most of the gaming development are now done with Middlewares like Unity and Unreal. The way I see it, more and more people will develop with Middlewares in mind, those API won't be touched by a shrinking amount of developers.