And it's pretty hard to find shooters that don't revolve only around scripted narratives and cinematic gameplay. Whether or not such a design concept is effective, ArmA (II) is not one of those.
In today's gaming world, the borders that define genres are dissolving. There are certainly instances where ArmA plays more like a real-time strategy (or real-time tactics) game than a shooter, and when was the last time you saw ragdoll in an RTS? This genre focuses on a larger scope than most shooters, and narratives and cinematics aren't driving characteristics of this type of gameplay.
Saying that standardizing certain technologies is part of moving forward with the gaming world is quite inaccurate. As the gaming world moves forward, more diversity appears in the tech as more advancements are made and ideas are explored. While it's true that a lot of game developers try to follow a standard, it's not so much the gaming world advancing but the business aspect of it staying put.
The gaming world is not moving forward in a linear path either, rather it is branching out in all different directions. There are still audiences for games like ArmA, and many of them are hoping BIS is doing their best to keep it from merging with those other branches simply out of obligation. Ragdoll isn't somethign a game like ArmA is in dire need of, and if the need should arise then let it come (and be resolved) on its own terms and not simply because everyone else is doing it.
As a final note, if someone believes they need ragdoll to satisfy their desires, then it's like you said, there are plenty of shooters out there with ragdoll; choose one.
I was adding on to reasons already listed, not saying they should do it soley because everybody else is. Also if you want Open world or RTS games with ragdoll check out AoE3, Company of Heroes, Soldiers heroes of WW2 1&2, Crackdown, Mercenaries1&2, DoW 2, etc,etc. Also the "if you want this feature then go play another game' excuse is crap. Everbody here has just as much right to ask for new features as you do.