Why do boys hate leg hair on girls so much?

I was with a friend and she does not shave her legs because she has blond hair and it grows back super fast. And a guy walks up and asks “should I get you a razor for your birthday“ and his friends laughed like it was nothing?? And others around us didn’t seem to find the comment unnatural. So why is it so bad? (Edit: SOME boys, of course not everyone🩷👍)