There are cultures in which it is considered impolite to look other people in the eyes. It is seen as rude and confrontational.
I can look my husband in the eyes, but other people looking at me unnerves me.
I am very tall for a woman, 6', so I am stared at a lot, particularly when I am with my hubby who is 6'5". We forget how tall we are until we are in a group of people and we can see over everyones' heads. So, needless to say we aren't looking people in the eye a whole lot.
I am also taller than a lot of men and they stare at my chest, which I guess means I get to avoid eye contact!
Tallgirl.