What ever happened to blinking NPCs?

This seems kinda random, but its been bothering me recently. Why have NPCs in Half Life 2 and its episodes stopped blinking naturally? (Naturally, as in they are told to blink in the AI code, and not through a vcd) I was watching some of the pre-release demos for Half-Life 2, and one guy mentioned NPCs blink relative to light levels. I remember thinking "that's an interesting feature, I wonder if they kept it." So I fired up Half Life 2, and all I got was non-blinking stares from the citizens. As I started experimenting with vcds I noticed the "AI_BLINK" event. I checked github, and apparently it's supposed to stop blinking. Through my searching of github I discovered code that made NPCs blink, but not in reaction to the environment. So then I thought "well maybe this code is never used, kinda like some ai features of the npc_crow."
Then I re-watched this video (Pardon the commentator):
https://www.youtube.com/watch?v=AbcXQ5eSYmI
Notice something?
This video was made in 2012, so what happened? Anyone have any ideas as to why and how? And if so, is there a way to mod the feature back in?
Then I re-watched this video (Pardon the commentator):
https://www.youtube.com/watch?v=AbcXQ5eSYmI
Notice something?
This video was made in 2012, so what happened? Anyone have any ideas as to why and how? And if so, is there a way to mod the feature back in?