Because you can do "systems programming" in them. What is "systems programming"? Roughly, writing OSes and the programs that come with the OS - compilers, lin

Because you can do "systems programming" in them. What is "systems programming"? Roughly, writing OSes and the programs that come with the OS - compilers, linkers, debuggers, databases, and so on. The distinction is between "systems" and "application" programming. Again, this is 1960s language. These days, there is a FAANG take on this. If I understand correctly, Google thinks of their software infrastructure as "systems programming". That kind of tracks with the old definition if you think of the entire company network as "the machine", instead of thinking about only one computer.