JSON and Erlang just don't get along in the way you'd like them to, unfortunately. Some of that has to do with how Erlang handles (or doesn't handle) strings. Some of that was that there was not a data structure that closely mirrored JSON's structure in Erlang up until Maps were introduced.

The problem isn't really JSON - JSON is an exceptional format for what it is supposed to do - the problem is that Erlang was created for a specific purpose and that purpose wasn't to vend out strings/JSON over HTTP.