A thought occurred...
Witnesses face a constant mental quandary (or have to do mental gymnastics), because every person they meet, talk to, interact with etc will all die soon! (According to the society's teachings anyway)
So this must play havoc as they try to keep an emotional distance from these ones. Effectively, people have to be "de-humanised" from a witness's viewpoint so that they don't feel bad when those ones are killed...
"Dead man walking"