Here's the thing, military doesn't want Lt to stay Lt. Up or out. Lt has to learn how all of the various machines work together on the battlefield if he wants to become a general someday. This means tanks, planes, and drones too. Not just rifles. When Stormin Norman designed a battle plan in the first Iraq war, he needed to know that Air Force would quickly achieve air supremacy, allowing him to maneuver his tanks to interdict enemy supply lines without serious opposition. He needed to understand logistics to keep his own troops supplied while denying supplies to the enemy. It was a quick victory because the Iraqi troops ran out of ammo quickly, and fled in panic. Air Force then bombed their troops on the road until POTUS said enough. A general needs to have sufficient academic skills to know how all of the war machines at his disposal work when designing a battle plan.
Wars of maneuver tend to be far more effective than wars of attrition. Afghanistan was primarily counter insurgency . Guerrilla warfare is a different animal. A general needs to know how to do both styles of warfare, which means mastery of various war machines.