What does it mean when people look down in the hallways when I pass them?

I'm really muscular, but not to the point of being gross, I'm 5'9". I have a kind face, usually smiling. People tend to look down as they pass me like their shy or scared and I don't know why. I'm not a mean person either and am relatively attractive.
What does it mean when people look down in the hallways when I pass them?
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