Is there a need to do apply_filter(‘widget_title’, $instance[‘title’]) or any other ‘widget_xxx’ filters?

I am reading the book Professional WordPress, and have code like

$title = apply_filters('widget_title', $instance['title']);
$name = apply_filters('widget_name', $instance['name']);
...

I wonder if there really are filters like widget_xxx? What do they do?

For example, it makes them editable using the Front-end Editor plugin.

All the cool widgets are doing it:

http://core.trac.wordpress.org/browser/trunk/wp-includes/default-widgets.php