Low Ready sucks with a full length battle rifle even when you don't have a bayonet fixed ...
I'll post a few from WWII of Soldiers with carbines or SMGs for comparison.
Bottom line, the actual combatant will carry any weapon based on the environment and type of danger likely to spring out of the foliage or countryside.
. In the movies, most scenes of battle ready troopers shucking and jiving down the lane with rifles pointed to the sun or slung on shoulders is used to make some movie point, other than the fact that they in fact are ready to be all killed in a snap of the fingers with their pants down.