[refulgentis]

Because it's arguably syntactic sugar and, IMHO, it's worked out better for developers for Dart to model it as a 3rd party library problem. i.e. have a JSONSerializable protocol, and enable easy code generation by libraries.

i.e. I annotate my models with @freezed, which also affords you config of the N different things people differ on with json (are fields snake case? camel case? pascal case?) and if a new N+1 became critical, I could hack it in myself in 2-4 hours.

I'm interested to see how this'd integrate with the language while affording the same functionality. Or maybe that's the point: it won't, but you can always continue using the 3rd party libraries. But now it's built into the language, so it is easier to get from 0 to 1.