OpenGL wasn't portable enough to be performant at the same time, for several reasons. I'm talking about Vulkan, not about OpenGL and its troubles in the past. Vulkan addresses the issues which you mentioned.
Vulkan still has extensions. The whole reason game developers want to have lock-in is so that you can squeeze the maximum possible quality out of a known set of hardware.
Once you start abstracting that away you are falling behind other companies who may be able to draw slightly more particles at slightly higher frame rates at slightly higher resolutions.
The whole reason Nintendo is still saying "we have Vulkan" is because they are the only console manufacturer were raw graphical performance was never the system seller.
DX has driver caps, feature levels and optional features within each feature level - so you have to branch on runtime anyway, just like with OpenGL or Vulcan extensions. Even Apple Metal has Feature Sets for exactly that reason.
If you want to evolve your API together with the hardware, you need some extension mechanism.
Lock-in doesn't cause you to be able to 'squeeze performance' out of the hardware. It causes you to specialize your code to the platform so much you can't port it to another.
It's the other way around. Developers don't care much about portability. The care about APIs that allow them to build performant programs. For them, a bad side effect of such APIs is vendor lock-in.
Why would a game developer want to limit his audience?
> Lock-in doesn't cause you to be able to 'squeeze performance' out of the hardware.
Let's assume GPU X supports some feature that GPU Y does not. Then you either use an (say OpenGL or Vulkan) extension to use it to squeeze out performance (lock-in) or you eschew the lock-in, don't use the feature and ignore the performance advantage. Now multiply this with lots of features and also consider that the graphic APIs of consoles offer some rather unique features that don't map directly to, say, DirectX11 or OpenGL.
Once you start abstracting that away you are falling behind other companies who may be able to draw slightly more particles at slightly higher frame rates at slightly higher resolutions.
The whole reason Nintendo is still saying "we have Vulkan" is because they are the only console manufacturer were raw graphical performance was never the system seller.