Having a back button has little to do with necessity and more to do with convenience and common sense. Without a back button, people are constantly trying to figure out where, and how to go back within each app because each app goes back in a different way, forcing the user to go any wild goose chase to find the back button. Going back is one of the most basic things that we have to do all the time while on a phone, and if it is always accomplished in a different way, it will cause the user to constantly waste time figuring out how to go back. Here are many examples. To go back you may have to: swipe up, swipe down, swipe left, swipe right, click on the upper left X button, click on the upper right X button, click on the lower left back arrow, click on the lower right back arrow, swipe up to first reveal a menu and then click the left arrow, swipe down to reveal the menu then click on the left arrow, click on the screen to reveal more menu options then click on the left arrow. Trying to figure out which one it is wastes time and requires MUCH more thinking and movement of the hand, diminishing user experience. To make things even worse, within the same application, there will be different ways of going back depending on which page the user is on within that application, causing going back inconsistencies even within the same application!
A back button also causes an issue with exiting certain functions within the same application. For instance, I am using Google Chrome right now and I want to close the keyboard after I am done writing this reply. On an android phone, all you would need to do is click the back button, but on the iPhone, there is no back button to close the keyboard, so now we try to figure out how to close the keyboard by looking for anything, and everything, swiping down and up in every direction to try to figure out how to close the keyboard, just to waste time finding out that this application requires you to click a tiny not easily seen done button right above the keyboard.
To make things worse we don’t even know what we are looking for, whether it’s a button, an arrow a swipe a hidden menu or a turd on the screen, we constantly try to figure out how to close things, cancel things and go back, all of which is handled by a back button. All we need to do is click the back button on android, and we are done. But to cancel an operation on iPhones, we need to figure out how to do that which is always done differently.
This clearly complicates the user interface even more. A back button is not a necessity, it is a common sense feature that needs to be implemented, just like a right mouse click is to a desktop computer.
