Most of my Rust projects don't need a JSON parser. You probably haven't been a programmer that long if you think JSON is "basic". If it was 20 years ago, you'd be arguing for an XML parser in Rust's stdlib. In 20 years I'm sure it will be something else. File/data formats come and go. The stdlib of a systems programming language shouldn't be taking on a forever maintenance burden for something that likely won't be in widespread use for all that long.
