Why aren’t guys or men subtle when checking someone out?

I have a male coworker that when we speak he normally pulls his chair back and looks at me straight in the eyes and then head to toe and then tilts his head and looks at my legs. Then he continues to look me in the eye for the rest of the conversation. I’ve noticed this and I find it quite funny that he’s not very subtle when he does it and he’ll do this maybe once or two times during the conversation but every time that I speak to him regardless of whether it was throughout the day or just once, if I pass by him he’ll do this.
Is this considered checking out? And if it is why aren’t men subtle when doing this?
Why aren’t guys or men subtle when checking someone out?
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