Speaking from the perspective of a user interface nerd, I found this blog post from Brad Ellis to be very interesting.
The UINavigationBar, navbar for short, has been around since the original iPhone. Historically, navbars have been convenient and clear, easy to understand and easy to build.
Then phones ballooned, enough that the iPhone 7 Plus supplanted sales of the iPad mini. Now, if you own a modern iPhone, navbars can feel unwieldy — literally out of touch.
Burgeoning screens mean the distance between the navbar and our thumbs has grown. The screen on a 7 Plus is so tall it would take a thumb-length increase of 150 percent to reach those pesky buttons with one hand. Just another knuckle or two. Nothing weird.
As devices change, our visual language changes with them. It’s time to move away from the navbar in favor of navigation within thumb-reach. For the purposes of this article, we’ll call that Reach Navigation.