1 Performance. C compilers have thousands of years of effort put into them. That's hard to beat. You could use some thing like LLVM, but its basically C anyways. You could go Go or D route which emit their own native code but it took years for them to get close to the vcc, gcc and llvm speeds.
2 Compatibility. C/C++ compilers are very platform depended LLVM can't interface with steamsdk on windows for example only Visual C++ can. Emscripton which emulate many of the normal C things only exist for C/C++. Android NDK only works with C/C++. And same thing with iOS. You would have to build native compilers for tons of platforms, some times not documented or priority platforms. Why? Just emitting C gets you there. 3 Ecosystem. Building on the compatibility, Nim does not have that many libraries, but C/C++ has a ton. Yes you can wrap any C/C++ with your a hypothetical native code generator - but thats a ton of work. With Nim it's a lot easier. You can nearly just include the headers. It's great. I have created many wrappers for C libraries that just statically link. At first I was skeptical, but it turns out emitting is one of Nim's strengths.
