I don’t think its dying. Hangouts are still being used by brands. Hangouts cannot be done without G+ profile. G+ community is little different that Facebook. Google Plus content gets better SEO signals and hence helps in ranking the content.
why should business use Google+ as a social media marketing Platform or SEO tool? Though Google+ has less engagement than other Social media platforms but every post gets indexed by Google’s search engine that your company publishes to the platform, which can help your content appear higher in the Google search results list.