I think the main idea why people don't play this in huge numbers is thats its just a hard / slow game --- I play games for entertainment, arma/2 was entertaining for a while, but once I found the limitations of the AI opponents and lack of any real atmosphere until the next massive gun battle, it became dull very quickly.
having said that, I still adore the game, but admittedly I just removed it from my SSD to free up space for other games :-) its just a bit slow and once it gets faster it falls flat in combat mainly from ? animations / AI being so chunky and non-fluid in combat that you become very aware you're not fighting opponents who act the same as you can? if that makes sense.
Its not even as if dropping you into a heart of a massive firefight is that entertaining in arma2 like you'd expect. Somethings missing there, maybe that it just doesnt matter that much if you die or not? which I guess is a very realistic approach to a war simulator, just isnt entertaining. :-P (the main reason people play games isnt it?)
Anyone holding out for Skyrim! thats kinda what i've progressed too now, atmospheric rpgs are a lot more inviting to take up my limited entertainment time :)
edit: I'll just tak this on, as was still thinking about this when I had submitted reply --- I kept arma cold war crisis? (that whats its called now?:P) on the SSD because the original OFP had that feeling which was so entertaining not sure what it was but something about it just made it fun to play / was really entertaining all the time even when just being driven places by ai in the back of a truck :-)