For me, it's that it's almost guaranteed a C++ compiler is available for the platform I'm targeting. This could be for various reasons, but it's usually either:

1. The chip isn't supported by LLVM (which most new languages use)

2. The platform owner /requires/ the use of their C++ only SDK and will not approve any other compilers for use on their app store, so C++ becomes the "machine language" of that platform.