Guys who open doors and lower their faces, why do you do this?

I'm not against it. Just that I usually just see this with older men, (near their 60's). Yet, lately I've noticed some younger men also are doing it at my university. Out of curiosity, for men who do this what's the motivation behind? Is it courtesy, basic manners, or do you instinctively do it?

Guys who open doors and lower their faces, why do you do this?
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