Every time you write a blog post you have one more indexed page on your website. This is just one more opportunity to help your business show up in search engines and drive traffic to your website through organic searches. It is one more indication for Google and other search engines that your website is active and they should be checking in regularly to see what new content you have.
Blogging also helps you get discovered through social media. When you write a blog post, you are generating content that users can share on social networks like; Twitter, LinkedIn, Facebook and Pinterest. This will showcase your business to audiences that may not know you until now.
Blog content also helps keep your social media presence ongoing. Instead of asking your marketing team to come up with new original content for social media (or creating that content yourself), your blog should serve as that source of new content. Strengthening your social reach through blogging drives new visitors to your blog page through your social channels.