That was actually mentioned in the article...

    So why is the BBC so good when most others are so bad? Maybe it's in the BBC's blood: The news
    organization originated as a radio station, where word count is at a premium and you must communicate
    clearly to immediately grab listeners. In a spoken medium, each word is gone as soon as it's
    uttered, so convoluted exposition confuses even more than it does in print.

    Ceefax (one of the few surviving videotext services) also helps instill conciseness in BBC's journalists.
    Text on low-def televisions has horrible resolution and only allows for a minute word count (somewhat
    like mobile).