the foundation of american society are based upon the government working for the people; that is how democracy works, so the military being controlled by the people is a necessity for the democratic system to function. there a couple advantages and disadvantages to this just like any system. the advantages being no wars the people don't want (in theory), no suppression of american rights by the military and the overall moral of the troops is going to be greater than that of a conscripted force because their fighting voluntarily. the disadvantages are during time of war, because if the war is unpopular troop moral will plunder, the army will have to draft soldiers in (this was the case during Vietnam) and if it drags on too long the fighting force will be severely weakened by a lack of new recruits. i hope this helped there's probably some grammar mistakes in this but the general answer/ main idea should the trick for ya