Another lesson gone over your head........
In 1970, I enlisted in the Army, for an 8 year enlistement. This one is true.
I was 5'10", about 125 lbs. The Army thought I was the PERFECT size for their needs in what I enlisted for. NOT to carry a SAW, not to be the grenadier, NOT to hump the ammo, but perfect for grunt and pointman.
One of my buds was 5'9" and 225lbs. They didn't plan on him at point or carry a M-16, they envisioned a humper, carrying the SAW or mortar, or even the radio.
Different jobs for different body builds.