Fair enough; this seems to be the most common complaint I've seen here. There's nothing stopping you from including colons, at which point it would look exactly like YAML and CSON, but then I suppose it would have very little added value beyond YAML or CSON. For me, the killer feature is chaining one-element maps on a single line (CSON can do that too, but it doesn't have unquoted strings).
While that might be convenient, it gives me a hard time comprehending what the actual structure of the map is.
I use json when I need to read it and messagepack when I need to send it over the network.