Many businesses know in theory that Social Media Marketing is important for their business, but a large number do not practice it.
They either underestimate or simply see it as irrelevant to their business. Those who do try, quit it after a few months not seeing the investment converting into sales. The point is that marketing is a process. Its a journey which you keep on tinkering and tweaking so that you find out exactly what works for your products and brands before you can make it work. Social Media Marketing is also cheap compared to traditional marketing.
Social Media works for almost all businesses and the ones who reap success out of it reap it with their presence at the expense of your absence.