As humans we rely on our senses to give us cues that preempt actions.
Visual awareness is 99.50% of the stress inducer it has to be as we react very quickly to what we see. If you do not see a threat because you did not look at it, how are you supposed to be the one feeding the ooda loop - terms used can be clarified if need be but they are specific to threats.
A man or woman needs to see the threat first before making an unconscious decision to react to it, of the possible presence of a threat.
If you are walking down the street and two guys walk past you laughing and smiling, you may not take a second look. If they walk by you and hands in their pockets and they are laser-eyeing you up and down you will have a drastically different response, I hope.
Eye contact does many things, specifically for you because someones intent can be projected by eye contact. I was in a class a long time ago and an instructor told us, "if you want to know who the baddest motherfucker in the room is, start eyefucking everyonex stare everyone down and if everyone looks away, you are the baddest motherfucker there
" That has real merit in many situations. The guy who wont look away in crowd or area you are not familiar with is probably the guy eyeing people up for a reason.