Explaine to me why .......................
Cos it limits the range of conditions you can use the camera in , for example needing a shutter speed to freeze some motion in less than stellar light. You can shoot wide open and the only real way of getting the shutter speed up is increasing the ISO , if 400 isnt useable cos of noise , then either you dont get the shot or you get an unacceptably noisy one. If 400 was noise free than you have increased the useability and utility of the Camera. PPL shoot at the low ISOs cos they CANT shoot at 400 without compromise.
The nicest thing about smacking your head against the the wall is.......The feeling you get when you stop