Answer:
It is a custom that there has been kept ever since.
Step-by-step explanation:
Custom is the name for situations where something is usually done, without this being determined in written rules. Many forms of etiquette and other codes of social interaction between people are based on custom. Customs of this kind can differ greatly between different countries and even between different places or social groups in the same country. A proverb that has its counterparts in many languages, says that one should "take the custom wherever one goes", so that when one is a guest with someone do as the hosts are accustomed to do.