Letting players create their own character can be a really fun an engaging mechanic. It allows for a lot of replayability and players are more likely to get attached to their character if they designed them. However, some games allow players quite a bit of control on how their character looks, but leaves out the oh so important choice of gender. As we know that nearly half of all gamers are female this is a pretty large portion of the audience to not represent in a game where the design of the main character is supposed to be left up to the player.
Examples:
Saint’s Row[]

The first Saint’s Row game offers a lot of customizing options, allowing players to choose their race, their build, and even alter their character’s features quite precisely, building them from the ground up. However, you can’t play as a woman, and it seems very strange considering that in all aspects other than gender your character is a blank canvas that you can paint all over. This problem was one that was clearly noticed by the creators so they changed it and allowed players to choose between a male or a female Boss in all the games that followed.