Vulkan has a much greater following in open source than commercially, which is unsurprising considering its focus.Vulkan (it's successor) is the first thing to actually work properly and even today (2021) only used in a small fraction of games and it's really only id that make it work well.
It's also a much younger standard than OpenGL and has only recently added necessary extensions to replace it in certain sectors like DCC.
Beyond that Vulkan 1.1 compatibility is required in any device implementing Android 10+, so it's installed base is already huge regardless of actual applications supporting it.
We can infer that this compatibility requirement probably means that the Android 10 UI code uses Vulkan to render it on the screen.
As for your "a small fraction of games" comment - using DXVK, VKD3D and more recently Zink the support in Linux for Windows games has massively increased due to the lower level nature of Vulkan allowing developers to use it as a HAL to implement another API like DX9 to 12, or OpenGL on top of it.
The general problem with Vulkan is that it requires far more developer investment to create a viable engine on top of it as the lions share of GPU compute management which is abstracted for OpenGL code requires a complete infrastructure in Vulkan.
While the downside is a lot of extra code investment - the upside is a far greater degree of control over system resources otherwise obscured by the driver abstraction with OpenGL, not to mention most of the time if there is a bug the chances are it is in your implementation in Vulkan rather than the drivers (as Vulkan drivers are also much simpler overall).
Were it not for Microsoft seizing on DX12 to create at least some impetus to move to Windows 10 then there would likely be far more support for Vulkan in Windows games - alas Epic clearly finds an extra backend on top of DX12 too much to bear on the Windows platform, especially when DX12 allows them to cover Xbox too.
Look outside of standard games though and you will find many emulator projects running Vulkan backends - Dolphin particularly from early on. but also PPSSPP, RPCS3, Cemu, Yuzu, Xenia, even the old PCSX2 was confirmed to be working on a Vulkan backend last year.
Not to mention nVidia's tentpole RTX real time path tracing demonstrator Quake 2 RTX was actually written with Vulkan and not DXR.
Albeit it initially used nVidia's vendor specific RT extensions prior to the vendor agnostic extensions being finalised upon RDNA2's release.
Oh and another thing, Vulkan also has a backend in ANGLE which translates OpenGL ES 2-3 code on systems lacking a OpenGL ES driver - this translation layer is in many Chrome and Firefox distributions as WebGL is basically web happy OpenGL ES.
The point being, for a standard not even 5 years old yet it is doing pretty damn well indeed.