Because Google+ is not just a social network– it is part of a powerful social platform that integrates with key capabilities like Google docs, chat, hangouts, gmail, and more.
In addition to the social benefits, there are powerful search benefits as well. Google search algorithms recognize social sharing, as each share tells them that the content is valuable and trustworthy. This is true regardless of the social media site, but it is all the more powerful with G+, since it ties in directly with Google search products.
For these reasons alone, Google+ is a high-value opportunity worth investing the time and resources required to cultivate it.
A common misconception is that Google+ is a ghost town. In reality, Google+ is home to vibrant, active communities that foster deep engagement. The trick is learning how to find and take advantage of these communities to build long-lasting relationships with core audiences.