Why do attractive guys avoid eye contact with me?

Whenever I walk past an attractive guy, actually not even only attractive guys but average and unattractive guys as well, they all avoid eye contact with me. They either look to the side so that I see their side profile, they look straight forward with their chin up while walking confidently, they look down or they just look at something behind me like a tree or a house.
On the other hand women make eye contact with me ALL the time, some will even be staring.
I don't understand why guys avoid eye contact with me? Am I unattractive or intimidating? Do I look mean? Why did guys do this? Because I wouldn't say that I am EXTREMELY attractive or anything, but I'm not ugly either. I don't dress or walk funny, so why do guys do this? What's the reason?
Is it to humble me?
Why do attractive guys avoid eye contact with me?
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