template_preprocess_page in a subtheme can't set title prefixes, suffixes or attributes

Here is a code sample:

function omsabot_preprocess_page(&$vars) {
  $vars['title_prefix'] = "fob";
  $vars['title_suffix'] = "foo";
  $vars['title_attributes_array'] = array(
    'class' => array('foo'),
  );
}

This does not show up on the site at all!