I was once handed a princess to use as a playable character in my first text-based chat roleplaying game with 3-5 other people of girls and boys.
It quickly grew on me and I started using girls more often as my playing character from then on.

I won’t deny that looking at them could be generally nicer, but I believe it’s not the main reason. At least when it comes to text roleplaying, I like to (try) think and behave like a lady in games, to roleplay in their world of view. It’s neat in its own way and I love the immersion when it hits me!