I guess the ability to work in really restricted/minimal environments where you only have a simple C compiler like tcc, and nothing like LLVM. Or paranoid environments where you can only use CompCert. Something like that.
I'm not talking about embedded, I'm talking about e.g. intentionally minimalist systems that have to be self-building, or systems that have to be built with a formally verified compiler (which does not exist for C++), or anything else like that.