[trashtester]

This is exactly it. And it's a much broader principle than just ransoms. Any organization/group that live outside of an established legal system depends on being seen as honorable if they want to have any relationships with other organizations/groups.

This applies to criminal groups (and individuals), clans in places like Afghanistan or Somalia and even to whole countries when dealing with each other.

Essentially, such groups are playing repeated games of Prisoner's Dilemma. They need to be seen as playing a tit-for-tat strategy. If they are known for playing always-defect (or always-cooperate), other "players" will (if rational) play always-defect against them.

This means they need to be honorable in that they keep their promises. But if someone disrespects them, they also must be predictable vengeful.