Google is the world's most used search engine in the world. Google+ which was a later entry, captured the social media world rapidly and is currently the second largest social media platform. For businesses Google+ is a source of referral traffic to your website and also an opportunity to have your brand page rank on search results in addition to your website, giving higher search ranking opportunities.
Google+ brand page influences the organic search results for your website. This means that if you have a Google+ page, and post frequent, relevant posts - your website could appear higher on the Google results page when people perform a specific search. The more recommendations, reviews and positive feedback you get - the more Google will realize you are a viable business, and will rank you higher on their results pages. After all, people turn to Google for reliable business information, and that can directly influence their buying behavior.