Kate Middleton, the Duchess of Cambridge, is also known as Baroness Carrickfergus. Doesn't exactly flow off the tongue, does it?
Carrickfergus is a town in Northern Ireland, and Queen Elizabeth made Prince William the Baron of it once he married Middleton. When they were proclaimed the Duke and Duchess of Cambridge, they simultaneously became the Earl and Countess of Strathearn, and Baron and Baroness of Carrickfergus.
Duke and Duchess are superior titles, so they're used more often. Even if they weren't, though, we can see why Middleton would prefer them anyway.
Better to stick with Cambridge and call it a day.
This article originally appeared on InStyle US.