We did evaluate the option of using Vulkan. So have others. It's not even necessarily off the table, we just don't think it is the best design approach.
If you are very interested in the details of API design choices, then I'd suggest joining the Community Group. Anyone can join!
Re:Apple proposes new web 3D graphics API
by pjmlp on Wednesday February 08, 2017 @02:55AM
(#13596622)
Which is a good example why I don't have any issues with native code on OpenGL ES 3.x mobiles, while Chrome with WebGL is just choppy and dropping frames left and right.
Re:Apple proposes new web 3D graphics API
by ThisIs_MyName on Wednesday February 08, 2017 @11:37AM
(#13599591)
Naw, that's happening because you have a JS thread doing everything. Native code on OpenGL ES is structured very differently.
Especially since things like NaCl exist(ed) which are inarguably lower level and still safe.
I think it's folly to create a whole new API before evaluating the option of using Vulkan.