unset($loggedin) in forumfome?

can you please make me understand why is not unset the the $loggedin variable in forumhome?
from my logic, it should be like that the code:

      eval("\$activeusers .= \", ".gettemplate('forumhome_loggedinuser')."\";");
    }
  }
  $DB_site->free_result($loggedins);
  unset($loggedin);

thanks.