Once a habit is established, it becomes a role or norm of action. Customs often involve binding reciprocal obligations. Also, custom supports law, without which it becomes meaningless. In the words of Maclver and Page, custom establishes a social order of its own so that conflict arising between custom and law is not a conflict between law and lawlessness, but between the orders of reflection (law) and the order of spontaneity (custom).
In general, customs regulate the whole social life of man. Law itself cannot cover the whole gamut of social behavior. It is the customary practices that contribute to the harmonious social interactions in a society which normal times of peace and tranquility. The influence of custom, at times, extends beyond one's own community. In certain communities custom determines the relations between two communities at war. The Bedouins of the African desert will never destroy a water-well of the enemy.
Some of the customs do not play any role in social control. They just exist because of their ancient nature just as all people bathing in an unhygienic tank or a lake just because of an established religious custom. Even the custom of performing Shradha in India has no meaning if people do not know how to respect what the past has given us as well as accept our moral obligation to the future generations. However, in most of the traditional societies the customary practices are all emptied of their meaning.
In brief, although custom is regarded as one of the less formal types of control like public opinion, its influence on social life is very significant as it alone contributes to the textual part of social behavior.