It's worth noting that it's still a religious thing as well. It's just that if you want to claim the governmental benefits that accrue to people the state consi

It's worth noting that it's still a religious thing as well. It's just that if you want to claim the governmental benefits that accrue to people the state considers married, well, you'll need the state to say you're married. And unless you live in a world where words can be owned by an entity, nobody "stole" anything. Many marriages still get both the official paper (civil contract) and the sacrament. They mean a similar thing, and humans being humans means they use the same word. (It's also not "usually the mayor", btw - that depends on the country. In Germany it's e.g usually the "Standesbeamte". A government official that does the job of a registrar. Mayors can only do the job if they've also been appointed to that role)