std.json: why no constructors

Why doesn't JSONValue have constructors for the types it can
store? Like these:
https://github.com/GassaFM/icfpc2013/blob/master/icfputil/icfplib.d#L76-L112

Or did I entirely miss the One Right Way to do that?

I know there is std.serialization on its way, but for now, it was
just more convenient to use what is already present in Phobos.

Ivan Kazmenko.