People who kidnap others… prison guards… soldiers who guard prisoners of war…
They must be exhausted.
I can’t imagine a job much more stressful than being responsible for making sure a prisoner or captive remains captive.
The person you’re guarding is most likely constantly plotting and scheming ways to get out of captivity. Most of those methods probably involve making a move while you, the guard, is gone. But I’m sure some of them involve attacking you when you least expect it.
And it’s 24 hours a day. It’s constant. You never know when they may make a move. You can’t really get a peaceful night sleep because that’s when they’re most likely to strike.
Not to mention that your captive truly despises you and probably wants you dead. This may be a bit less so in a prison situation, since there was a whole court process and vetting before you ended up there. But in general, I can’t imagine, even in a prison, there are many situations where captive and captor are good friends.
I’m not even comfortable when someone at work has a personal grudge against me. I can’t even imagine what that’s like when someone wants to… no, has to kill me to gain their freedom.
All in all, keeping people captive just doesn’t seem worth the trouble.