I remember my very first FRPG game session. My first character (priest/healer type) died in the first room. So we rolled up new characters and went back at it. Second character - a mage type - put the spiders who had killed the last character to sleep and we won the first room. While they were asleep, I killed them. Every time I put something to sleep, I used my dagger and “cut his throat”. It was just the thing to do. Now I did question my GM the first time. I asked if that was OK, and he assured me that I could still be a “good” person and slit throats. Well I’m not 12 anymore and I don’t agree.
Do we have to always kill people in FRPGs? Look at the classics, stories like the Three Musketeers and Ivanhoe. They don’t always kill the bad guy. OK, sometimes it bites them in the @$$, but sometimes it works out for them. I wish that there was a little more surrendering in games, and less slitting of throats. Maybe a little capturing. But why would a FRPG character not kill someone?
1 - Ransom. The main income of low born knights was the capturing and ransoming of enemy knights. It got so out of hand that there were battles where one side would be losing their forces because they were off protecting the prisoners they had already taken. If player characters can make money, they can be incented to do things.
2 - You don’t want to be cold blooded. In my campaigns, if you cold bloodedly kill people, it affects your Carousing and other social skills. Psycho killers make themselves known, even if it is just that cold or crazy look in their eyes. Want to be the face man for the party and talk to all the locals? Better not be slitting throats.
3 - Because like begets like. In other words, if the campaign world is built on the idea that ransoming and capturing are the way to go, then if the party is ever overwhelmed, they don’t need to be killed. They can be captured. Maybe there is someone who can pay a ransom - Maybe one character is released to gather funds. I have successfully captured an entire party and forced them into indentured service - making them perform three missions for their captors. They were both mercenary forces in a merchant war, so there was nothing personal about it.
4 - Because people you let live owe you. If you think you’re going to try this, let the first guy they let go give them something. Maybe he reveals an ambush, tells them who the secret enemy is, appears out of nowhere to show them a secret passage when they are about to get their butts kicked, whatever. If the first time they let someone live, he comes back with a bigger force and attacks, then they start thinking, “Well that was stupid - should of killed him.” So be overly generous and hope to convince them of the new normal.