Our skin is very sensitive to stimuli and rubbing your feet together is one way in which you can reap the reward of stimulating sensitive nerve endings on your feet.
Comparing cricketing with hand-warming techniques like rubbing your hands together or blowing into them, Dr. Paolo shared that such physical movements can activate “the parasympathetic nervous system resulting in immediate cardiovascular relaxation and other stress hormone benefits” (via Sleepopolis).
Getting to sleep in a relaxed manner is a lot about mindfulness too. This is probably why some people count their breaths. Rubbing your feet together might also help you stay in the present and consciously focus on your body, which is something clinical psychologist, Dr. Lauren Kerwin told Well+Good. “Those who cricket while they fall asleep, which is common, do so often to improve their sensory processing of their body lying down with blankets around them in a dark and quiet space,” explained Dr. Kerwin.