In my campaign, everything is constantly going badly. The Source has been destroyed, devastating the local region. The main hardhold was shelled with white phosphorous. Almost all of the NPCs (including NPCs that players invented for their playbooks) are dead. I've found that I am constantly having to invent new NPCs, since the players have started genocidally destroying any conflict. I think this is largely because they aren't developing relationships with NPCs. When I bring in new NPCs, only the Skinner, Chopper and Child-Thing are open to having relationships with those NPCs other than "I don't care about them" or "I want to kill them". Only the Skinner and Chopper develop meaningful relationships, the CT's relationships are all just "he brings me treats", "he finds me weird", et cetera. He has never fought to protect an NPC or worked in an NPC's interest.
Two PCs (Chopper and Skinner) have 3 or 4 NPCs they care about. But they will genocide anybody outside of their tiny group. Two of them don't care about any NPCs and generally resist any attempt I make to create NPCs that have backstories with them. One of them (the maestro D') doesn't really care about the game at all (girlfriend of one of the players) and just likes to use Just Give Me A Motive on any NPC she can. Her response is usually "I don't know" when I ask her what her relationship is with an NPC I'm inventing, what her crew does in her establishment, or whatever. I'm thinking I should recommend she switch playbooks since she doesn't really care about establishing who her crew is or what they do. She has basically just turned her maestro D' into a poison-mad loner who sits in her bar alone and drinks, and occasionally rolls to remote-control murder people for slighting her.
The move says "someone who might conceivably have ingested something you've touched" - perhaps her establishment should start developing a reputation for causing people to drop dead? I don't want to nerf her move, but I don't like that she is just murdering NPCs with no repercussions or real story motive.
The other one (the Driver) doesn't establish relationships even if I suggest them. "What's your relationship like with your dad?" "I dunno, I guess kind of detached." I can never get him to answer a backstory question with anything other than "I sell him drugs" or "I don't care about him". He doesn't save NPCs, fight for them, or really do anything proactive other than joke around and go on psychotic vision quests. I don't really know how to bring up this problem with him, or otherwise maneuver him into situations where he has relationships with characters. I think the best thing would be to use respond to "Open Your Brain" with something that commands his character to care about other people. He is very receptive to drastic character changes due to psychic experiences.
What can I do about this issue? Do I just need to keep inventing NPCs until they find some personalities they attach to? Do I just keep bringing in new threats from elsewhere whenever they annihilate the current threat with high explosives? How can I develop threats that they won't want to solve by poisoning / fighting / blowing up everybody?