Blogging is a major part of any online bu siness, most businesses that have a storefront or product pages dont really have a good platform on their site to have updated content. Having a blog will allow them to get around this.
Posting new content will help in a number of ways, for one posting new content will keep Google Happy and also reach out to new potential customers. Another benefit of adding new content to your blog is by giving you even more options for your social marketing. A lot of people share their new content on facebook, twitter and Google + not to mention the hundreds of other social marketing platforms that are out there.
Another benefit of adding new content for your blog is for SEO, also known as search engine optimization. You can target new keywords by adding new posts. Overtime you can end up with 100's of new keywords that have been targeted in your new content allowing you to rank for these keywords. A similar service that offers this is a Blog Posting Service.
Lastly the major problem with people adding new posts comes down to a few reasons. One is they may just not have enough time to write new content, or they do not have ideas to write new content. The internet is out there to help you with both. Getting new ideas can be as simple as browsing other blogs that are related to yours, from there you can build on your own ideas and come up with new content.
If you dont have time you can always outsource your content, but usually this option does not meet your expectations. When you write the content yourself you can always tweak it to how you like.