I picked Civ/Rebel because there is a variety of things you can do, without having a void of no action to fill (although this tends to happen sometimes)
I also couldn't agree more with the explanation @Sagebrush, on why the biases of white-listed can ruin the experience of new comers, and quite frankly people who have been on the server for a while, including myself.
I will also add on by saying that, I don't think that everybody does this intentionally.
I think that the "Ego Driven" Culture that was formed by the civ factions, bled into the other factions tainting the role and the way they conducted themselves within that role. Let's be honest not everyone is a "career cop" or R&R, eventually people who join the APD or R&R are civs that play with a civ mentality, with only stricter rules and less chances to fuck up. What this creates is a "culture bleed " and no longer the APD and R&R consist of the Police genuently trying to stop crime from occurring, and the R&R to Rescue and Recover everyone who request for the help willingly (Obviously unless you are denied). I cannot begin to describe the amount of times I've seen the apd witness a player killing another player, a player robbing another player, a player having an illegal weapon engaging and killing other players right in front of them, and then going over to the player who has been killed and making an arrest because they had a small bounty. The amount of times a medic has not done what I've asked of them because their friend was fighting against me. This is many times the result of people who play mainly civ, do when they join other factions. They don't play their role they only occupy it. Now I'll be Naive to say that I want people to become a real life police officer or Doctors or just simply put "RolePlay", I honestly understand that wouldn't be fun and the server is not build for it, but this server is also not build to be a King of The Hill. People only join the whitelisted factions for money. If you're reading this tell me you've never heard a friend that is in the APD say something along the lines "Alright I am going to go make some money I am broke" It's gotten or has been for a while depending on how long you've been playing, very toxic, not fun to play, not new player friendly. I think this is part of the decline of server population, although I know is not the only reason. Arma 3 is a fairly old game and it's popularity dwindles from time to time. But when trying to keep you server alive, you have to balance two things, one [ how do I maintain the people already "in" happy, and those who are new hooked ] This server lacks both to be honest. I am not disconnected from any of the things I've just said, I am guilty of this behavior, maybe that is the way we are meant to play the server? Anyways those are my 2 cents, this is my opinion, yours might be completely different and that's okay. Feel free to reply I am more than welcomed to hear your opinion.
Also If you are wondering why I wrote this twice?, It's because I had to literally copy and paste over to notepad and write it there, because to go back and fix something you wrote on this website is scuffed I don't know.