Many Joomla!® website owners have businesses that consume their time and attention at the expense of other things, like family, hobbies, and living a life. Often that means they have no time left to participate in social media sites. We have observed a not-uncommon attitude among the site owners that social media sites are largely a waste of time and resources, and that they would prefer not to spend precious time and resources to participate. Largely, they haven't established accounts on even the largest and most dominant social sites.
One issue with that attitude is that if the site owner doesn't stake out an account in the name of his brand, someone else might. A competitor, an ex-partner or employee, or worse, an unreasonable and highly annoyed customer might just do so. Clearly, nothing good can come from that.
Once you have accounts on Social Media sites, it is pretty easy to set up some automated procedures to post attractive attributed links from every Joomla!® article on your site to each one of the social sites on your account page.
You can also display social share buttons on your pages which will allow your site visitors to post the same high quality formatted posts to their pages, thereby spreading your message at no cost or additional effort on your part.
Facebook is powerful, ask your mother.