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 
I distinctly remember ADSing on an AR in Halo 5 when I tried it out briefly, like it stuck out in my mind for how weird and out of place it felt
Maybe I'm misremembering things
it literally does not have ironsights, 5 and infinite do have a slight zoom with LT (that in 5 adds holographic HUD effects) but no ironsights, some weapons use scopes with that input instead but its a virtual scope built into the HUD. the zoom on non-scoped weapons works nearly identical to RE Village in the OP image, where the screen zooms in and the weapon slightly shifts closer but is not centered. The pistol in 5 is almost held in an ironsight-using position but is held just underneath the HUD crosshairs at an angle
I know the lore reason for why guns like the Halo 1 pistol have scopes despite no scope being visible on the model. Actually I think in Halo 5 you could stick different attachments to your guns, one of them being some sort of ACOG dealio you could put on the AR, making it feel more like a gun from COD, which is probably what I was thinking of.
Besides, in older Halos you couldn't even zoom in with non-precision weapons, it was all hipfire or nothing
yea 4 or 5 had a microtransaction situation with unique weapon variants, some of them had scopes that worked like the other in-game virtual scopes