If you improve your public speaking skills, it can help you to move on in your career. You'll be more confident and you can increase your chances for promotion.
According to Brian Tracy, a renowned motivational speaker, many professional speakers start in their companies. Or they're asked, from time to time, to deliver a presentation to some other professionals from their industry.
Often, thanks to a positive response from the audience, these people eventually get into speaking because they realized they enjoyed it.