Its almost an written rule for any mobile app to have a mast image/ text at the top the screen.
There is no reason for its existence, especially on content-driven apps where space is always a major constraint. There could be two reasons why that top header exists. First, someone thought it was a good idea from a branding perspective. But what is the idea behind branding when a user is already inside and using an app?. The second reason maybe that people are used to putting that thing for desktops and laptops (all having bigger screens) and simply forgot to take it out when designing for mobile and small screen devices.
Take that header out and use it to provide more content to the user. There is a reason why Google is much more than an engineering giant. Chrome’s mobile app does exactly this. This is what I experienced when I was using the Chrome app today.
First, I opened Firstpost and notice the address bar is present.
Now, I scroll down and the address bar is gone. This gives greater space on the screen to show content.
Now I swipe upwards and no matter where I am on the page, the address bar appears.
One word – Google!