By creating a blog that is of value, you can attract an audience and eventually convert them to customers, partners, friends, or otherwise. Having a blog and writing about important topics that are relevant to your audience establishes yourself as an authority in the space. It enhances your professional image.
A blog is meant to generate awareness about you and your brand. It's best used as a tool to establish authority and make people trust you. Popular blogs like Problogger or Social Media Examiner are business blogs that made the business of blogging itself work for them. They sell advice on how to blog.