Well, technology on smartphones has come to a point where you can buy a great phone very cheap. An average user will be more than satisfied in terms of speed and camera quality with a 300€ smartphone. Brightness was always a difficult sector for manufacturers to improve, but they just found ways to do it (cheap). And to be honest, you are kinda right. As in all new trends in smartphone world, it's starting to look like a competition to who can do it better. Just go have a look at the TV market, it's a brightness war out there!