In terms of gameplay mechanics, old school zoom aiming achieves the same thing as ADS. Is getting to press your nose against virtual firearms really that important in a game about shooting werevolves and vampires?
I blame this on the proliferation of Call of Duty over traditional scifi and fantasy shooter franchises. You can fucking ADS on an assault rifle in Halo now 
Me, when I entered this thread for the first time expecting some noncontroversial
dunking merriment:
ADS struggle session fuck yeah
I've got 3,000 hours in arma. While you wear tearing the kingdom i was studying the accurate ballistic modelling of some made up gun "designed with input from cmmg". The very serious gun company that iirc produce tactical canned bacon at one point.
I'm more of an Unreal Tournament ridiculous rocket acrobatics type, but I can appreciate the sheer dedication that ARMA goes through. It isn't just "we have rusty fences and name-drop US military weapons" realism pretenses. It even has the "be bored for hours BE FUCKING TERRIFIED FOR A FEW MINUTES" experience of actual combat, from what I hear.
We used to call it a hiking simulator.
It's like hiking in Nova Scotia, a bit dangerously close to Sunnyvale Trailer Park, where shit could go down at any moment, especially if the Big Dirty goes wrong and the heavies are called in.