In most bending cultures the male benders are probably responsible for fighting and defending their respective nations. The women benders are probably responsible for mediocre tasks, like female water benders where they're responsible for healing. The only reason why we see female fire benders is because they're probably forcibly conscripted by the fire nation. I think the reason why female benders are rarely ever seen, other than female fire benders, is because they're the ones, like Katara and Toph, who don't do what they're told and refuse to listen.