Because men & women are still overall looking for something different, that's my 2 cents. What you say about the romance publishing industry is roughly correct although your algo description flattens the diversity of the genre (note the popularity of shapeshifter novels, paranormal, Amish with no sex, etc etc; there are many subgenres). What you don't note is the distinction between romance and erotica. Romance has a story with a happily ever after. Can TikTok or Instagram AI Boyfriend ads provide a story satisfactorily?

I'm not sure if research has really addressed evolution of women's expressions of sexuality over time and changing social norms. Even in the romance genre, what's considered appropriate in terms of consent and fantasy has evolved quite a bit over the last 40 years. That's true in terms of porn aimed at straight men as well, though not necessarily in the same directions.

But anyhow, how would AI boyfriends continue what's popular about romance -- the customization (subgenre for every taste), the story, and the happily ever after or happy for now for the woman? The last part in particular doesn't seem to be relevant/considered in the AI girlfriend discussion, it's just not part of the structure.

Also, dating sims seem to be popular in some geographies and not others; I know nothing about them, so there's got to be a story there...