Last year I looked for JSON output with the dig command on Linux but found the yaml option while reading the man page. It was handy. I always wondered why yaml/JSON output is not standard with Linux and Unix utilities for scripting needs. Anyway:
Because neither yaml or JSON existed when most of these tools were written, and then people got used to the current outputs, and so it's very varying whether or not anyone has felt the pain enough to decide it's worth adding the option for another output format.
