remove page_top & page_bottom from theme info

Is it safe to remove page_top & page_bottom from custom theme .info file?? or it's required for every themes.

function system_system_info_alter(&$info, $file, $type) {
  // Remove page-top from the blocks UI since it is reserved for modules to
  // populate from outside the blocks system.
  if ($type == 'theme') {
    $info['regions_hidden'][] = 'page_top';
    $info['regions_hidden'][] = 'page_bottom';
  }
}

// Render page_top and page_bottom into top level variables.
  $variables['page_top'] = drupal_render($variables['page']['page_top']);
  $variables['page_bottom'] = drupal_render($variables['page']['page_bottom']);

Seems like it injects page_top&bottom to every theme even it's not defined.