Even if C++ is faster to run, the difference isn't big on today's computers. That's why on mobile devices where cpu and memory are rather limited, C/C++ is still widely used.
But think about development times instead. If it takes 2 months using C++ and 1 month using C#, which would you go for? And when big modifications/refactoring need to be done, a higher level language makes it significantly faster and easier!
