I just read the following:
"Prince William has been made Duke of Cambridge, and his wife the Duchess of Cambridge, Buckingham Palace has said. The prince has also taken the titles Earl of Strathearn and Baron Carrickfergus, linking him to Scotland and Northern Ireland."
And this:
"While the Prince of Wales did not take any additional titles when he married Lady Diana Spencer in 1981, he was already Prince of Wales, the Duke of Cornwall, Duke of Rothesay, Earl of Carrick, Baron of Renfrew, Lord of the Isles and Prince and Great Steward of Scotland and Earl of Chester."
So perhaps I'm a bit naive, but all this... stuff... is important?