I was the TL of the libraries for almost a year, and there are good reasons we didn't go this route:

- it adds overhead. Being able to write JSON.encode(customer) would mean that every class needs to retain its field names. Minification could still work if this information is stored on the side, but it would add overhead.

- it doesn't make sense to automatically encode elements that cannot be decoded. You should have: x =~= JSON.decode(JSON.encode(x)). (where x =~= y means that the two objects are Json-equivalent).

- The Dart-Editor already provides a quick-fix to write a toJson for you. To be honest I'm not really a fan of it, since I believe that serialization information should be outside the object, and not in the object (that's what "toEncodable" is for), but that's another story.

- It's extremely easy to get the behavior you want. Just use (or write, if none exists yet) a package that has your intended behavior. This is really a one-line change... This way you pay the price when you want to, and don't force it on all users.