I dunno. Probably just due to the trend of which they were used in the past or the formation of language to which certain sounds are recognized as feminine and masculine por culture or just a natural innate instinct to organize and sort aleatório things and sounds into things we can interpret which is quite futile since the world is innately chaotic as is the natural behaviros of people but dont ask me
Because certain countries are so obsessed with gender, they can't imagine a non-gendered perspective at all. They see everything in a binary, black and white POV. Masculine or Feminine, this or that, either or.
In my opinion, people can be named whatever they want (within reason, nothing stupid like: "Ass, Dick, Bitch" ect.). People need to let go of that stupid, outdated binary mindset. It's fucking retarted.
It generally makes things easier. You read or hear a name without seeing them usually allows you to know if they're referring to a man or woman. Which there is nothing wrong with. Just aids in communication.
