Chaos is "freedom" and "power", but usually only for the guys on top. Somehow, everyone lower than them are strongly deluded with their chances of success. I mean, when did a single cultist achieve anything worth of note? While on that, when did a single CSM achieve anything of note? It seems that whenever one of them falls, everybody is like "that guy was a dick, anyway, moar power to me". So no matter how you look at it, only the guys up top benefit from all the teeming masses of crazies. Especially since books show that pre-CSM people are oft unwilling converts. But who'd follow those gods willingly? I mean, Khorne, I sort of understand, some people are ax-crazy and want to kill stuff left and right. But it's not a very promising in chances of survival. And what do you do on your down time? Tzeench is more like it. Knowledge, power, spending all day making spells to hack Facedataslate and all. But you can be easily justasplanned dead or mutate. And do Thousand Sons make new rubric marines? And how? Nurgle is for absolute lunatics. I mean, there are people out there who like being sick and, say, want to catch AIDS, but really? Who the hell wants to spend their life so rotten with plagues they don't really feel pain anymore? It's like: "All glory to Nurgle!" "Uh, your nose fell off!" "Noses are for the weak!" (let's not forget the Purge with their stupid ideology of killing everything, making them slightly smellier JRPG antagonists) Slaanesh is probably the easiest to grasp for a simple person, but only because they're junkies in space. Maybe not for actual drugs, but the thing is that they will never have enough/find the ultimate high. Kind of sucks to be them. Of, and no matter who you serve, you might turn into a spawn or a demon might gib you when spawning. So... yeah. Why would anybody follow chaos?