They're also there to fill archetypes. As Jinx herself put it best, regarding DoaF, "Pumpkin the cute one, Shauna the mom, Freya the whore".
That was purely based on who was in the top 10 posters, and could've been 10 females or 0 I did notice it at the time and thought it was funny though. I also strongly disagree with Jinx's assessments!
Rosa the wife/mother (in TAY), Porom the child, Rydia the whore