>>104018I can speak for English countries, but not specifically for Germany. His perspective is probably different, but I have the outlook of a historian and lawyer on this matter.
Common law marriages were the law for centuries in anglophone countries until they were abolished around the year 1900 (at least in America) to force the emerging migrant Catholic Church out of power over the family. During medieval times, the church held absolute power over family law, but the reformation saw this power transferred to common law in England. When Irish and Italians started pouring into the country, there was a massive political fight with protestants trying to keep the Catholic Church out of the family (where it could influence politics). Similar things happened across the west during the 'progressive' era. Therefore, the government made marriage a contract with the state on the state's terms, and, due to statist marriage law, this is typically seen as favoring women with no-fault divorce etc. Previously, marriage was a sacred and unbreakable covenant between man, wife, and God as the major partner. Any obligations not met would result in severe penalties through the church magistrate.
It's also pretty disgusting how the state uses marriage. It simply becomes a tool for controlling family life and people's conception of it. This trivializes the family as a minor partner to the state and reduces marriage to a dissolvable 'promise' with no obligations, which is horrible for man, woman, children, and society. In this case, the only advantages to the official documentation are what the other posters mentioned, which are important depending on the 'inheritance laws' in your country (also very corrupt in their intent).
His perspective is valid, But you ought to consider a primary and secondary nature to the marriage. If you are first married in a binding covenant of faith, then simply signing a court document is only a secondary and unimportant action requesting acknowledgement from corrupt overlords.