In the end, all computers be damned, it's the infantry man/ tanker who gets the job done.
Yes we saw how well the Ash and Trash defend themselves in fire fights. Half the weapons jammed from lack of maintenace in the ambush during the main offensive.
As for bullets and beans, the point of it all is, every single branch of the army/airforce/navy is there for a single purpose: support the Army & Marine infantry and tankers who are the ones who at the end of the day either win the battle or loose the war.
Because until a grunt or tanker is standing on the ground and hoisting the flag, you really haven't won jack crap.