Chaos worlds do have a civilian populace that basically just lives day to day lives like anyone else in 40k. They're ultimately slaves, but the vast bulk of Chaos adherents know they need to keep the chattel around to do basic work for them, so apart from a few particularly psychopathic individuals who flay their slaves for funsies at random most just ignore the mortals working their fields and mining their ores.
The Iron Warriors in one book have mortals perform almost every task in their army and civilian roles, largely because they lost a lot of marines to infighting and are too proud to ask for reinforcements from Medrengard. Humans grow the food, enforce the rules, man the defences, repair their machines, process the dead, culture new workers at the embryo farms, guard their prison (with one inmate), mine their resources, man their factories and every other task needed. The marines themselves largely hang around their main fortress, govern and bicker. With a few exceptions the marines only kill humans when they have a reason to do so, such as needing human blood to sate their daemonic artifacts.
Huron Blackheart's space fortress in the Night Lords books has a huge civilian populace. They have markets, bars, prostitutes. Hell they even have fruit stands! The place is dangerous, roamed by psychopaths, the odd daemon, and occasionally the odd crazed marine out to kill for what entertainment they can get out of mortals, but people still live there in vast amounts and grow stuff, make things and barter with spacefarers that berth at the station and the human raiders that serve Huron.