The problem is that when you work on big teams and are forced to work in C++98 with lots of style guide restrictions. Or when management will ever allow for updating the compilers on the build infrastructure.

Also compiling C++ code in C++11 mode won't make many developers use Modern C++, instead of C compiled with a C++ compiler, as many still do.

Maybe it works for your context, but in a global context we need to have safer languages for systems programming. Which were already available when C didn't had any meaning outside UNIX.