Earlier quoted context omitted.
The amazing thing is that you can potentially write all your code in C and have backend/frontend logic for the web, Windows, Windows Phone, OSX, FreeBSD, OpenBSD, Tru64, VAX, Arduino, Linux Kernel, Windows Kernel, Mach, Hurd, and practically every processor or operating system ever built, and even iOS/Android (via Xamarin). Wow. You can even link to and reuse that code from languages such as: C++, C#, Java, Ruby, Per…
C# is a much higher-level language than C, with a much richer set of libraries that can be relied upon to be everywhere. That's why it matters.
Citation please. AFAIK, there are significantly more C libraries than C# libraries.