Maybe the women raiders in Fallout are the ugliest so they get used as cannon fodder?
Jokes aside, a mod for customizing raider groups to be more distinct in look and behavior for New Vegas actually seems like a good idea. Ones closer to NV would probably have more women in them and better gear. Include AI modifiers. Make groups closer to the city more terratorial/toll extortion based and wasteland raiders more aggresive and opportunistic.
Implement it using the existing raider group categories and the player can customize the gender/gear/behavior differences between the groups with sliders and percentage values or something. Can't find anything like it so far on nexus, but I might just be missing it.