I dunno. Probably just due to the trend of which they were used in the past অথবা the formation of language to which certain sounds are recognized as feminine and masculine দ্বারা culture অথবা just a natural innate instinct to organize and sort যেভাবে খুশী 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 অথবা Feminine, this অথবা 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 People need to let go of that stupid, outdated binary mindset.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. আপনি read অথবা hear a name without seeing them usually allows আপনি to know if they're referring to a man অথবা woman. Which there is nothing wrong with. Just aids in communication.
