The warfare in the game is meant to emulate that of the Middle Ages, and so, too, are its basic rules. Why kill a major or even minor lord or commander of a large group of battle-ready men when you can capture them and hold them for quite the profitable ransom—the game lets you turn this against the various NPC lords, for that matter, further reinforcing the whole fact that, much like real medieval history, war was little more than a very bloody, exciting, and on occasion potentially fatal game for those in any degree of power. Still, you'd get some scars and even lose some teeth, either way.
The Surgery Bonus: Most deaths in medieval warfare (that weren't from disease or starvation on the march) were from battle wounds that today would be easily treated (rehab's another story entirely). That's right: in the middle ages, if you didn't die from dysentery or left before the fighting actually started, chances were you'd get stabbed or cut, then die because medicine wasn't advanced enough to deal with gangrene or infection. A good real life example of this is Richard the Lionheart; an otherwise routine crossbow bolt to the shoulder became fatal because his surgeons botched the operation, causing gangrene, infection, and then death.