And there's an indirect advantage related to social media. In a way blogging is a form of social media in itself, since you use your blog to share content and readers can engage with it in comments. Rather than just being a uni-directional method of online publishing, it's interactive, conversational. You also share other people's content in the body of blog posts, or by linking to them.
So if you get into blogging, add content regularly, link out to and quote other bloggers in your posts, as well as reply to your commenters, you'll already have a good idea of what social media is all about. So if and when you do get into using Facebook, Twitter, Google Plus etc for marketing you'll "hit the ground running" so to speak.
Also, a regularly updated blog will supply you with something new to share on these networks. If you're a non-blogging business person you can still use your social networking accounts to get clicks to your website's various pages, of course. But if you've only got five or six of these to tweet over and over again that soon becomes boring for your and your followers.
If you're constantly sharing your own new, comprehensive and informative blog posts on the other hand, that makes your stream more interesting to read as well as create. You'll get lots of click-through traffic from these shares, and your authority will build much more quickly than if you were only sharing other people's articles and blog posts and your own occasional and necessarily brief insights in the form of tweets, Facebook updates and the like.