iPhone automatic updates is a puzzle
In the "More about Automatic Downloads" section: 


  If your iPhone, iPad, or iPod touch has an Internet connection and you
  turn on Push Notifications, your content automatically downloads to
  your device. On an associated device that doesn't support Push
  Notifications, your content automatically appears in your iTunes
  download queue. You can manually download the content in iTunes.


I had turned off push notifications for the App Store and automatic updates stopped working. After I turned it on again it started working as usual.