NPC is insufficient in humanization. Let's think about some problems sensibly.
War is cruel, but most people want to live. If lords know that they would suffer from long imprisonment or beheading after being captured, they would be more cautious about the battlefield. If lords doesn't want to die, surrender or retreat will be the two most likely options, unless the enemy is their father murderer. Small clan mercenaries are less likely to fight to the end, because living is more important than money.
In warband, when you ask what lords are doing, lords may answer that they are pursuing a lady, or collecting taxes in villages, or resting in the city, or patrolling nearby... Check the list of conversation events of Lords, and you will find that they have plenty of things to do. At present, in bannerlord, they are almost only seen recruiting new soldiers, plundering enemy villages or following in the army.
I don't want to say any more. The experience of bannerlord game is very different.