Why do you guys not properly supporting DX12?

49.04% of all Personal Computers in the world run Windows 7 - DX12 - No,Vulkan - Yes
Windows 10 is only 26.8% - DX12 - Yes,Vulkan - Yes.
Linux,Mac OS X,Windows XP,Windows Vista,Windows 8,Windows 8.1 - 20.56% - DX12 - No,Vulkan - Yes
69.6% of the Personal Computers in the world Do Not Support DX12,but support Vulkan.
(True to June 2017 OS market share)

It doesn't worth the effort to develop with DX12,
Vulkan supports almost all OS'es,Including Android.
The only games that support DX12 only are Microsoft's games...
Both are based on the Mantle API anyway.