“Oh she even has three names.
How quaint.”
Yes, it’s “obligatory” to have a middle name when you’re “important!” It’s a little more forgivable when you are a married woman who may well have had a professional career before marriage. But mostly it’s personal self-agrandizement.
I generally am not a big fan of the three name thing.
Why the sneering? You are either very young, born after the time when most people got married heterosexually and the woman took the man's name for the sake of the children's sense of family unity; or you've never lived in a big city or been a member of a large virtual community, where there might be 12 people named "Amy Barrett"—hence, a differentiating middle name.
Many family surnames are extremely common, like Smith or Brown, and most European-descended first names are also common because they are cultural or Biblical, like John, Matthew, etc. Therefore, middle names are a practical measure.