I agree with you there's no wind or rustling, but, no conversations? I can't name the number of times I've passed groups of people and overheard conversations between two (usually two, maybe more sometimes, but I haven't noticed it) NPCs. Actually, there seems to be weird glitches with that where you'll trigger one, walk away, have it Doppler fade, then WHAM, next line will be at full volume and will not shut up until the ambient has run through to completion, even if that means overlapping with a quest dialogue cutscene you're doing. :P
That's my biggest complaint, because most of the conversations sound like they were written by a retarded 4-year old and are much more annoying than they will ever be entertaining. The fact that I can barely hear it when I'm close doesn't bother me, it's when i get 40 meters away and it starts blaring again that it really gets under my skin. Don't even get me started on the static discussions drowning out conversations I'm trying to have with mission NPCs.
TBH, getting rid of the static NPC conversations would be a plus for this game, not a detractor.