It may be along the lines of wishful thinking trying to have a more captive audience than in a browser. A browser has things like a home page, back button, bookmarks etc that are easily accessible. When you're in the app, everything points to more stuff in the app. One large metric appears to be engagement, its harder to track engagement in a browser than a dedicated app. Anything that keeps you engaged is good, anything that may lead you away is not. But its just as easy to hit the home button on a phone as well to get to the next thing.