I think, it was just one top feature of the first standard C library. It made printing a lot easier. In standard Pascal or Modula 2, you still had to print every single data type with its own special "WriteX" statement. Even there was a distinction between "WriteString" and "WriteLine", the second wrote a string and added a Newline after it (I am not sure in the moment, if it really took a string or just wrote the NL). In printing to screen, some languages of those days where really spartan.