There no known reason for this, belief is habit, turning to addiction. No known side affect have been associated with this,
but chalk is produced in a non sterile environment.
Although it isn't an epidemic by any stretch, people do each chalk, and like anything else, it can become an addiction. Just like anything else, it's mostly a mental addiction more than physical.
No, usually the person is missing some vitamins and minerals in their diet and they are craving it and the chalk tends to satisfy the deficiency they are lacking.
