The Orcs aren't a subtle race. They like war and are built for it. Their hugely muscled forms are almost immune to disease and can survive wounds that would be fatal for almost any other race. Couple this with their total disdain for any election campaign more suble than a severe beating and you have an army of violent monsters led by the biggest and most psychotic of the lot.
No other army in Warhammer can match the diverse (but all maniacal) troop types of an Orc and Goblin force. Greenskins suffer from Animosity and have many of their own specialty troops and rules. As such, the army tends to stretch out of a commander's hands at some point in nearly every game. Wily generals learn to expect and exploit this battlefield maddness rather than (hopelessly) trying to control it.