Apple has released a new version of iTunes that makes some significant changes. "The new iTunes focuses on music, movies, TV shows, podcasts, and audiobooks," says the support page. And as a result, it no longer manages your iOS apps or Ringtones. iTunes U content has been moved to Podcasts and Internet Radio can be made available in the Sidebar. There are also accommodations for some new social features coming in iOS 11.
I suspect you'll be hearing (or making) some complaints about the iOS apps and Ringtones changes.