There are differences between being a product marketplace and a platform marketplace... the article touches on what might happen if Apple loses their status as the preferred mobile platform:

<< Android’s growth has far more important implications than just bragging rights. Developers tend to make apps for iOS before coming up with a version for Android. If Android continues to show up on more devices, the order could flip. As of 2013’s second quarter, Apple’s App Store generated 2.3 times more revenue than Google’s app store, Google Play, according to App Annie, an analytics firm. But Google Play had 10 percent more downloads overall. It’s one thing to cede a portion of the market because it’s racing toward the lowest possible price, but what if that market becomes the center of gravity for the entire industry? >>