When was that ever a part of the definition? It was part of the early Unix culture, sure, but even many contemporary OSes didn't ship with compilers, which were a separate (and often very expensive!) piece of software.
OTOH today most Linux distros don't install any dev tools by default on a clean install. And, ironically, a clean install of Windows has .NET, which includes a C# compiler.
OTOH today most Linux distros don't install any dev tools by default on a clean install. And, ironically, a clean install of Windows has .NET, which includes a C# compiler.