I don't get it. When I was in the army,and AFAIK,going back to Revolutionary War times,"Cook" was an army MOS,just like mechanic,infantryman,medic,truck driver,etc,etc,etc.
And it wasn't optional. If you were assigned to go to "cook school" after basic training,being a cook was your official army job.
If there is a shortage of cooks,it is the army brass that is at fault.