@Lonewonder08
@Banesephy
It's because the manga are intended for the sort of people who are shy, unassertive, sorts of people. Japanese teens/young adults are actually doing stuff with people of the opposite sex and actually having sex. Otaku are basically nerds, if they could have sex, they would be instead of reading manga.
It explains why so many of the women in these manga are always either, nerds, dishrags, violent, or crazy. That's what women seem like if you're too young, or too shy to be able to see them as something other than these strange beings that act with no apparent motivation. They're not really human to you, and it shows in the writing.
It's not the mangakas fault though. The editors are the ones either allowing or more likely demanding that female characters fall into these stock categories. Remember too that Japan is HEAVILY into tradition, and even today, a lot of old-boy establishment-types don't think of women as actually people. Is it far-fetched for the publishers themselves to hold those opinions and for editors to go out of their way to encourage the mangaka to conform to that standard in their writing?
Manga that have well thought out, reasoning, emotionally stable female characters with depth are rare. And I think you'll find that the publishing houses that produce those manga will be younger than the ones that don't.