sql query ther isn't condition access <> 0

this code is used by the module user list and use u.access <> 0 , why?
when an user can to have this value=0?

$result = pager_query("SELECT u.uid, u.name FROM {users} u WHERE u.status <> 0 AND u.access <> 0 AND LOWER(u.name) LIKE '%s%%' ORDER BY u.name ASC", $number, $element_override, NULL, drupal_strtolower($op));