Swearing is not pointless, but serves a ritualistic role. It has been used as a psychological mechanism that shaped societies and history. And it still does so, as evident in this article. Swearing an oath is a contractual ritual and is the basis for all lawgiving in the English language. It was used as a binding contract between kings and their subjects (you can look up the Salisbury Oath for just the tip of the iceberg on this topic.)