The article is talking about "married" as the opposite of "single." Whether you're legally married, or "functionally" married is somewhat besides the point. (Although, as a pre-packaged set of rules governing economic partnerships between two people, marriage still has a lot to offer. E.g. if you keep a 9-5 to pay for health insurance while your spouse throws herself at a startup; you'd be daft not to have some sort of arrangement in place to share in the upside if she is successful.)