We now have the scientific evidence to back up those claims. Research conducted by Greg Feist of San Jose State University found that when people let their focus shift away from others around them, they're better able to engage in "metacognition," the process of thinking critically and reflectively about your own thoughts.
Where things get tricky, though, is figuring out what to do in order to encourage metacognitive thought in the first place. When we're routinely overwhelmed with outside noise, carving out space for unstructured daydreaming takes planning, structure.
Sometimes the most productive periods of contemplation come to us unawares and don't last very long—but that doesn't mean they aren't useful.