By using a modern language, having a C++ subset as shading language, SDK with support for fonts, texturing, 2D, math library with SIMD support, input devices, model loading, a debugger than can even go through shader code.

Instead of having to play "go fish" for libraries of various quality and support levels.

By the way, this applies to same productivity offered by Apple, Sony and Nintendo 3D APIs as well.

If you read the article properly, the only place where Vulkan is getting traction is on Linux.

Even on mobile space, Samsung and Google keep trying to advocate it, because being optional and with only Pixel and Samsung S devices having good support for Vulkan, no one is really bothering to use it, when considering targeting the widest user base.

https://vulkan.gpuinfo.org/vulkansupport.php#android_devices