@pheonix Something else I hadn't considered that helps explain why these apps get made, perhaps even initially in good faith, is that many mobile users are reluctant to use web browsers. Their app store is the first place they look, rather than a web search engine. A publisher that doesn't want to miss those readers will therefore want to show up in the app store.
And then the "benefits" of a more publisher-controlled experience would make them want to direct their web users to the app too.