I don’t want to wait on language releases to get updates to json, regex, etc. Nor do I want a crappy stdlib impl of something to become widespread just because it comes out of the box like Go’s worst of breed html templating and http “routing”.
Python's json is an often-quoted example of why not to have it in the standard lib. There are some bad defaults that no one can fix for stability reasons. Though I admit it does come in handy sometimes.
In production, I've lately seen serde_json backed python implementations, this makes sense for performance and memory safety.
