For some people, repeating a simple action before bed can create a sense of comfort and security. Similar effects can come from reading, drinking tea, listening to quiet music, or using a familiar blanket.
This is closely connected to how habits influence the mind. When a person repeatedly performs the same calming activity before sleeping, the brain can begin associating that activity with relaxation and bedtime.
That may explain why someone could genuinely feel that the foil is helping them sleep, even though the material itself has no established sleep-enhancing properties.
