Performance? Lisp can give you that, as can OCaml, Haskell, and other better languages. Real time system? There is a mountain of research on real-time garbage collection and on using HLLs for real-time systems. Operating system kernel? OSes were once written in Lisp, and OSes could conceivably be written in other HLLs.
Throw in a requirement to interoperate with a C library and suddenly things get ugly. Yeah, sure, you have an FFI, but debugging across a language barrier is difficult (I have had to do it, it is agony). Suddenly you need to worry about pinning objects so that the garbage collector won't move them while some C library expects them to stay still. In some cases your code basically becomes C but with the syntax of an HLL, and you start to wonder why you did not just write that routine in C to begin with (it would have made your life easier). Performance matters but your compiler needs to set up a trampoline so that your code can provide some kind of callback, and now that is a bottleneck that kills all that other optimization work. Then some joker writes some C++ code, and the rest of your week is spent writing wrapper functions because your FFI cannot deal with the name mangler.
At the end of the day there is no particular technical reason for C or C++ to remain so popular, and a big pile of technical reasons to stay away from such languages. C made a bit of sense in the 1970s when computers were small and the understanding of compilers and programming languages was less well developed. At this point C and C++ are a liability that we are all stuck with. Maybe some day the expense of sticking with C and C++ will outweigh the expense required to switch to better languages, but I am not holding my breath.
