I don't understand why having the fingerprint sensor in the back of the phone (Nexus, Pixel and some other android devices) never took off that much. Ever since I got it on my Nexus 5x I absolutely loved it (Pixel now, same thing). It's incredibly intuitive, works both right and left handed, doesn't take up screen space, and they've just added a "scrolling" feature to open your notifications by swiping it. Seems like a no-brainer, I can't see any fault in it, and yet very few phones have it.