The first edition of “The C Programming Language” was published in 1978. Developed by Dr. Dennis Ritche, Dr. Ken Thomson, and writing support from Dr. Brian Kernigan completely changed the way we program forever. C was a revelation, a shift from the paradigm that each mainframe and computer had to be run on unique, separate operating system. Through C, Unix became the primary OS of academia and thus would be the foundation for Apple, Windows, Java, Python, C++, Go, and so many more tools we use today.
Hello World was not some blub thrown into the wind a new developer could do, it was meant to be instructive, while also being a short, fun thing. Hello World introduced the core ideas and concepts in C that you needed to know in order to get up and running right away. #include statements, strongly typed functions and variables, return statements for functions with declared types, the whole works were there.
Hello World has taken off since then, being the standard way to introduce a new programming language to a developer.