I believe there are two distinct types of gamers when it comes to these matters.
Gamer A) the in-game avatar represents me. this is my story. these are my actions.
Gamer B) the in-game avatar represents someone else. this is a story. i influence their actions.
i'm certainly gamer B. even in a game with the silent character and a first person perspective i still never think of it as me. as such,.. when given a choice i almost always pick female avatars. i feel more invested in female companion than a male companion. it's the same in my personal life where i have a lot of female friends and very few male friends.
i imagine gamers in the A category would want a character that looks like them,... correct sex, color, and build. i'm sure it helps a lot with their immersion. i completely get it even if it is not for me.
