First thing my friend. The pacific was not set during WW2 D-Day, you might be thinking of band of brothers. The Pacific was the US/Japan theatre
I don't know much historical reasons but logically it must actually hinder an army to do this. With all the tank traps etc on the beach you would need to see where to shoot the mg's etc and also where to advance. Otherwise they would be spraying bullets through smoke and you'd have no idea where it was coming from. I actually think it would give the Axis more of an advantage in that respect
My second reason would be that the beach was being shelled by naval ships constantly... They may have appreciated visibility in this scenario considering how many of their own men were on the beach