Why does the drop function return false for http://jqueryui.com/demos/droppable/#propagation example?

Why does the drop function return false for http://jqueryui.com/demos/droppable/#propagation example?

For this demo;      
http://jqueryui.com/demos/droppable/#propagation
 Why does the droppable drop function return false? I took the return out and it did not seem to affect the behaviour. Ideas? 
<script type="text/javascript"> $(function() { $("#draggable").draggable(); $("#droppable, #droppable-inner").droppable({ activeClass: 'ui-state-hover', hoverClass: 'ui-state-active', drop: function(event, ui) { $(this).addClass('ui-state-highlight').find('> p').html('Dropped!'); return false; } }); $("#droppable2, #droppable2-inner").droppable({ greedy: true, activeClass: 'ui-state-hover', hoverClass: 'ui-state-active', drop: function(event, ui) { $(this).addClass('ui-state-highlight').find('> p').html('Dropped!'); } }); }); </script>