I spent years as a mobile developer and the thing that always drove me the most nuts was being handed a software design with lots of tiny buttons that were nearly impossible to tap with a finger. I generally implemented the UI by increasing the size of the tappable regions (without increasing the apparent size of the buttons) making it actually usable, but one time the designer discovered that I was doing this and went apeshit and convinced the project manager to order me to undo all this and make the tappable regions the same size as the buttons. The grounds for this was that implementing the larger tappable regions would take too much extra time - despite the fact that this had already been done and it took additional time to undo it.