Comment by Someone

The way I understand this: doing this in your application requires you to have network access, which means you have to convince your user to give it to you.

This gives you a way to count installs (and almost nothing else; you probably can assume arrival times correlate with time of installation and learn something about your global user base from that, but that’s all I can think of) without getting any permission from the user.

Applications can still use the old approach, but that’s more work and won’t produce accurate install counts. Apple thinks the end result will be that fewer apps will do it, making the dialog asking for network access rarer, and users more wary of giving the permission.