Eddy Cue and Phil Schiller, Apple executives mentioned that the App Store algorithm was tweaked to lower Apple’s own apps from appearing at the top of search results in an interview.

Wall Street Journal and the New York Times revealed that Apple apps were showing up quite frequently for the most common keywords, i.e., a ‘music’ query would list Apple apps in the first seven spots of the ten available.
On July 12, Apple had tweaked the grouping feature, and many of its apps dropped from the top rankings as a result. Maps and Video searches only showed one Apple app, while Apple Wallet was ousted from the top for terms ‘credit’ and ‘money’.
Apple mentioned that the handicap allowed other developers to gain a foothold in the search results. The grouping effect is still in place for other third party developers.
The Cupertino-based company mentioned that their stance on the App Store as an open, fair market for app developers remain the same.