What is the issue with the trailing comma of JSON Object

Usually i am creating valid JSON objects like this:

{
  hasPermission: true,
  notificationStatusId: 1
};

ON VSCode, when is save the file, sometimes it's adding a tailing comma automatically after the last property like this:

{
  hasPermission: true,
  notificationStatusId: 1,
};

Actually I'm not asking how to disable that behavior and i know how to do that. i am asking what is the reason VSCode has that feature of adding a trailing comma automatically?