Responses
Because men won't be interested and there won't be enought women to make the manga be able to keep going :) Boobies and sexy protagonist is what makes everything sell.
haah? You never heard of Astro boy? There have been plenty of male only robots series before, but they are sort of out of fashion these days. There have been tons of male cyborg/robot/machines in earlier sci-fi mangas/novels, but people eventually got tired of them.
Why is it the gender of a machine or weapon is always a girl???
Why can't it be a boy for a change...