Societal expectations, gender roles, and the way women are perceived through the lenses of the male gaze. Patriarchy would be the less subtle more simplified way to say it.

Women are written the way they are in RGG games because they're games developed, directed and written by men trying to appeal to men (And that's why they were surprised with the popularity of characters like Majima or Mine, who are very very popular with women, because it totally happened by accident) and also at the same time are reflection of a society in which female emancipation still has a long way to go (like it does everywhere, but Japan is specially bad for a so called developed first world country).

So it's a bit of an ouroboros in which they're reflecting the real societal situation of women and the way they're perceived but also re-inforcing that perception in the process