Why do we need to write the entire config data within update hooks?

Here's a typical update hook where we need to update the default config of a view provided by core:

function somemodule_update_1007() {
  $data = array(

    ... 100s OF LINES OF CODE HERE ...

  );
  $config = config('some.config.file');
  if ($config->isNew()) {
    $config->setData($data);
    $config->save();
  }
}

I have always found this to be very annoying, because a) a dev has to convert the contents of the .json file to an array (to be used as the value of $data), and b) we are adding 100s of lines of code to .install files, which makes them unreadable.

Why are we not doing something like this instead?:

function somemodule_update_1007() {
  $new_config_file = backdrop_get_path('module', 'somemodule') . '/config/some.config.file.json';
  $data = json_decode(file_get_contents($new_config_file), TRUE);
  $config = config('some.config.file');
  if ($config->isNew()) {
    $config->setData($data);
    $config->save();
  }
}