Social Signals are important for organic rankings because they are a trust signal. If you have a social presence, with engagement it is more likely that your site will be seen as legit. I do not feel as though social signals are as important now as they were say, a year ago. It is too easy to manipulate. You can buy followers, cheat engagement and build a reputation completely unrelated to your industry. While it isn't quite as important, it is still a ranking factor.
Social media doesn't need to be a complete waste of your time. Use it to stream customer reviews, industry related articles or advertise promotions. The social signals feed off of engagement. How many likes, shares, comments and reviews your business has on social media is what is important. It doesn't require someone to spend countless hours sharing pictures from the Walking Dead or commenting on every selfie. It requires engaging your audience however possible.
Your social media profiles are also reinforcement for your local listings. The name, address and phone number on your profile can be used to confirm you are who you say you are.
To answer your question simply, yes, social is important. Google plus, Twitter and Facebook are probably the most important. You have to prove to the engines you are a legitimate site and can be a trusted source for searchers, social is part of that equation. It isn't just about traffic from social sites.