There was a website and there was a manager. The manager wanted to please his boss. His boss wanted the manager to put a cool video on the website. The manager asked the web designer to put it there. The end.
Because it's particularly easy to publish to the web, things tend to get published without too much though about the who, what, why, where or when. Because there's so much on the web, competition for eyes is immense.
As the web has matured, so has the need for focussed, specific and meaningful content. To deliver a great experience to your users and value to your business you are going to need a content strategy.
I am going to write-up one example my team developed for The Open University Help Centre shortly. In the meantime, I can highly recommend Content Strategy for the web by Halvorson and Rach.