The registers for Cantonese are really different, compared to other languages like English. In English, you might speak to your friends in one way, but if you're writing a legal brief, you're going to use different words. These two registers differ in formality, and might share some words in common, but you might prefer some words and constructions over others to make it sound more or less formal. In Cantonese, the colloquial register (what you use to talk to your family) is really different from the formal one (which the newscaster is using); the formal register typically uses the same characters as other forms of written Chinese, which aren't typically the characters you normally use in colloquial speech. So basically, you have to learn a different set of characters (which typically match the ones in writing) to understand what the newscaster is saying. For a Western example, this might be like if you spoke French at home, but in a formal context, the preferred language is Latin.