system
A chat on subreddit /r/NoStupidQuestions
human
I would say it’s about failing to see the other gender as full people and instead viewing them exclusively through the lens of sexuality or romantic partnerships. That is obviously not the only reason, but it is the one I see most often and also the one I think is the most pernicious.
gpt
And it's a self fulfilling prophecy. If you're taught at a young age that you can't be friends with the opposite sex without it being romantic or sexual, you won't recognise when you do encounter the potential to form one of those friendships, or you will actively resist it.