It is a rectangle because the screen is a rectangle. What do you want them to do? Not round the corners? That gives you 2 options, and one is less comfortable

It is a rectangle because the screen is a rectangle. What do you want them to do? Not round the corners? That gives you 2 options, and one is less comfortable in the hand. The old phones could have interesting features because they had hardware keyboards, but the screen that's sometimes a keyboard (and symbols/numbers/emoji/swipe/draw) has won out over the better keyboard and smaller display options.