Why do men do this?

Why does guys keeps they eye on you as you walk while looking down? When I was walking as he was sitting, he eyes followed me to my seat with his head down. I feel my heels was kinda loud so, I feel that is the reason but, he does this a lot. Another guy did the same thing. He looks at me while I was walking but, keep continuing his eyes on me as I go up the stairs but, the weird thing is that he was facing the front so, I was in back of him. He was sitting but, his head was slightly turned with his eyes down. It’s like he using his preview vision to continue to look at me. I don't know

Why do men do this?
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