Granted, it came from there, but that was back in the days of map=eval(json) and they're gone. There is nothing in json the format (as opposed to json the language construct) to impose the unordered behavior.(Or, for that matters, the 'no comments' bit).
It's got nothing to do with parsing. The json comes from JavaScript syntax, where objects represent unordered mapping. Json naturally does the same.
If you want expressive power for reading, json is very poor in comparison to pretty much everything else. Just use it for simple serialisation.