I always felt that NPCs should be suject to things like hostage situations, slavery, etc at the very least.
Even if players were subject to slavery, shackles, binding, etc there could be mechanics like popping your thumb to slip out of metal binding or through the amount of strength you have to wiggle out of binding until you are free are just a few ideas on how to make it viable.
I think if there were escape mechanics for any situation that caused you to pop your thumb, arm, etc out of the socket combined with anything potentially being a lockpick if you break something or just picking up objects as weapons anyone could become a slave or hostage and escape eventually.
Surrender to potentially save death or spirit loss is a choice like anything else. And NPCs most of all should have some aspect of self preservation through surrender to continue on rather than just die for no reason.
And besides there could be various situations that come with fame for choosing mercy over killing for certain religions but also situations like slavery that presents a fine line between ransoming captives and treating them fairly or poorly or cultural and affinity infamy hits or grevious outcomes for people who do so that if they are in any leadership position could lead to riots or uprisings that play well with RP or gameplay.
Players could free themselves, others, liberate their comrads, pay ransoms, or buy the freedom of enslaved npcs.
Also in the case you are binding a criminal to face sentencing decide where the closest jail is if the criminal is wanted in multiple domains which arent in the place they are caught? Or if you have to go far out of your way based on the terrain which could take you out of the way to finally turn them in.
Or how the game would determine how someone is even friendly. If you are in the middle of nowhere and multiple groups are fighting and the person helping you saves you but is not a friendly but picks you up and their safety point is not actually safe to you but is part of your kingdom, duchy, county etc but is not really friendly.