I can't watch TV without seeing either a "Make Google do it" ad for Google Assistant or an ad for the Google Pixel or Chromebook. Google runs a metric ----ton of ads for their products.
Now mind you, nobody buys those products. But they definitely market them.
Because it's good. When firefox started slowly killing xul and the clusterfuck called IE stopped being the top (rabid) dog, a new kid had to come along.
Google+ seemed like an afterthought, a way to create a facebook clone without creating a facebook clone.
Google's basic strategy seems to be to throw shit on the wall and see what sticks.