The blog of your website gives you the opportunity to do two things: one, you can speak to your customers in a different, more approachable way. Two, it indicates to search engines that your site is active and an authority figure about your products or services. Many businesses do not use their blog section very effectively, if at all. This is a shame seeing as it gives you two main benefits!
The whole point of search engine optimisation is to show Google/Yahoo/Bing etc that your site is a worthy recommendation for information about your topic/brand/product. One thing they rely on is the constant or regular updates to the site to show it is still active – a good blog will do just that and more, allowing you also to communicate more freely with customers and prospective clients, showing them an insight into your world.