That actually is helpful narretei, because part of what I'm struggling with is how to keep things interesting when my natural inclination is to play most NPCs in a fairly reasonable fashion.
I think this is going to depend on your fronts and what particular scarcities you are trying to emphasize for your apocalypse. NPCs can be reasonable but that doesn't mean you suddenly have enough food or water, or that everyone knows how to work together amicably and becomes immune to disease. Also, when you have real power (and some of your NPCs must have real power) sometimes it is reasonable to leverage that in ways that fuck over other people.
I have a similar tendency, and certainly my players in the past have noted that my apocalypses tend to be relatively mellow -- there's not a lot of direct conflict and violence, but there's still a lot of serious problems that are not that easy to solve.
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For example, the last game I ran was an urban environment, cold, lots of snow and sudden cold snaps/storms -- and drinkable water was a scarcity, because for various reasons drinking melted snow was a really bad idea. There was however a barely-working water treatment plant that supplied most of the locality's water. The guy who ran that plant had real power. Having that power and understanding that he had it made the guy act like he had diplomatic immunity; he wanted to use the power he had to get more power, and when one of the PCs interfered with his attempts to do so, he reacted poorly and pissed off the PC.
But when the PC in question (a Maestro D) decided to take revenge, and convinced another local bigwig to attack the NPC who controlled the water filtration plant -- rather than stick around for a losing battle he blew up the plant and went into hiding. Suddenly nobody had any water, except the water they could get from melting snow.
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Which is all to say, as has been said in other threads: NPCs that are useful are NPCs you can't just kill. If all your NPCs are thugs, who exist only to do violence, then your PCs can stomp all over them, because their only leverage is the threat of harm and PCs are far better at dealing with (and dealing) harm than NPCs.
But if your NPCs make shoes, or fix machines, or know how to read, or control food production, then not only is it a bad idea to kill them but
they themselves understand that fact and, if push comes to shove, will use that fact as leverage against the PCs to get what they want. Sometimes vindictively (as above), sometimes not.
Reasonable people with power use that power to consolidate their position and make themselves safer -- and they do so at the expense of others if necessary.