By my math, a 4k laptop screen needs to be 20" diagonally before the pixel density drops to a perceptible level. Any smaller than that and the pixel density is

By my math, a 4k laptop screen needs to be 20" diagonally before the pixel density drops to a perceptible level. Any smaller than that and the pixel density is so great that I don't think you are getting any improvement to clarity at a typical laptop viewing distance. 20" laptops are a pretty rare occurrence today, even in the desktop replacement space. Most laptops I see with 4k screens are 13" to 17". So my question is, why waste GPU cycles (and by extension, battery) driving all these extra pixels?