Tooth decay proliferates in contact with sugar and bacteria in the mouth. When the crown is seated on the tooth, all decay is sealed within the crown. Hence, proliferation of decay is stopped. In that way, these crowns are superior to fillings, where secondary decay may occur at a later stage.
Kids love these and so do parents. Since appointments are less stressful, kids are more likely to have good experiences and develop a good attitude towards dental treatment as adults.