There ARE stories for all the female characters. But we do not have them because we do not have the all ages version of the game where the sex scenes are switched for the conversations.
Wish they'd add it, because as much as i love collecting sex scenes that i'll look at once, never masturbate to, feel satisfied with having gotten, and then forget, i would love to get the conversations and some lore.
And to further build onto what i mentioned first - DMM even has a character challenge for some characters which when completed (requires said character to be AW'd) grants you a third scene/conversation.
That said, i do not find the sex scenes stale. Perhaps because i do not really read them or use them. I just find it fun to get the scenes, go "yup, this looks nice" and then hit the skip button. Don't underestimate a collector's spirit! Checking a random CG site online destroys the collecting fun. Yes, i know i'm weird.