People still write regular shaders in languages that are much more C like.
People writing GPGPU code are few. Most of the DL GPU use is in Python through several layers, and in the end you are running hand-written SASS assembly sitting in an NVIDIA DLL or whatever.
I guess some people must think it's handy to have C++ support in GPU kernels, or they wouldn't have added the feature. But for it to drive technology, hard to believe.