Easy. A hyphenated name indicates the person was raised in a liberal household, with liberal values. Can you just see an emasculated man saying "Sure, honey, you won't take my name because of the oppressive patriarichal power structure that enslaves women? Well, let's use the hyphen honey, is that OK? Honey, schnookums?".
The woman was no doubt raised WITHOUT a normal, manly father figure, and WITH an angry feminist harpy for a mom.
If my GF ever said that she would not take my last name, the relationship is over before she puts the punctuation upon her reply.
...NEXT!
The mayor of LA took it a step further, and even changed HIS name. His was Villar, hers was Rigosa, so they both became Villarigosa.
Then he had an affair with the local Univision info-babe. Going to be interesting to see how they deal with the name at divorce time.