For me I use C because it's the de facto system programming language for botb Linux and Windows. Another reason is that C grammar is simple (but has a lot of quirks I do admit.)
Professionally I do Python. From my experience the breakages occur due to an over-reliance on libraries to do trivial tasks. Do you find a different case?
Unfortunately I'm not professional enough to answer this question. I use C to learn system programming only and I never had the capacity to look at the kernel.