Instead of asking, "how can we add social to our product" they should be asking, "how can we make our product more useful." They're clearly trying to solve a business object and not a user need.
I think it's disingenuous to presume anything else.
Just because you personally don't think you need this, doesn't mean the companies involved aren't trying to solve what they perceive to be some users' needs.
It looks like Bing is trying not to clutter the UI with its social features by default:
"Sidebar is the most novel component of the new Bing. It's a mellow, gray sidebar that is closed by default. It shows a thumbnail of your picture and two control icons, and that's it. There's a hint arrow to expand it. When you open Sidebar, it shows you stuff from social networks that's relevant to your search."