IBM annually does a consumer study in the U.S. Basically the gist of it is.... I think most everyone who purchases anything from milk all the way up the chain understands that at this point we have anywhere from 12% to 20% growth in the market in terms of stuff from organic, to non-GMO, to fair trade. However, people can't differentiate between things. People are over-saturated with this idea and by companies who say they do good, but in fact do something very different, as people discover when they turn on the news.
So B corp is a way for someone to know definitively that a company makes an impact on the environment, makes a positive impact with people, treats their workers well, etc., and that this is something you can take to the bank, as opposed to nebulous claims that we're a family company, but which perhaps has adverse effects in the community.