Why do supposedly straight men stare at other men?

So I work in plant like environment and I have guy’s staring at me all the time. I’m about 6’4 , slim with a beard and a decent amount of visible tattoos (hand neck and arm ) I get gay men staring a lot but they’re gay so I know why they’re staring in most cases but why do straight men constantly stare at another guy? Are they intimidated? Its like they will literally seek out eye contact and most the time it’s from shorter/smaller guys. It just seems weird honestly and really annoying.
Why do supposedly straight men stare at other men?
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