Yes, yes. And we could also have everything as binary. Now, UNIX people decided long ago to use plain text to communicate between processes, mostly because it's infinitely easier to read - and makes it possible to edit by hand if you need to. Have to interface with a REST API which consumes JSON and you want to do some testing? Open your text editor anywhere curl is installed, and you're done. That's pretty damn convenient.
No doubt they both have their benefits, however in an environment particularly suited for working with JSON, like node.js, the additional overhead of a YAML (or other) parser may not be desirable.
