Usually I play RPGs as a generic nice guy boy scout type, with a possible exception for kleptomania. Usually RPGs are written encouraging this, and I'm going with the flow.
Occasionally I try playing an evil character but I have trouble sticking with this. I carve out exceptions for NPCs that I like and next thing you know I'm saving kittens or whatever again.
UR pushes you pretty strongly toward playing a self interested survivor. You can be an extra nice guy if you want, but it's extra work and you aren't getting any medals for it, as you're told in so many words. There are no good guys, everybody's in it for themselves, and you'd better be the same. By the time I get out of Junkyard I've murdered several people who never gave me any trouble, just cause I know there's something in it for me.
("Curse those Protectorate imperialists!", he muttered, dragging M'Lan's corpse out into the cave, away from the light of the outpost doorway.)
A lot of post apoc games promise grittiness, but if they deliver at all it feels forced: INSERT GRITTY SCENE/MORAL DILEMMA HERE. In UnderRail it's perfectly natural. I can't think of another game that pulls it off as well.