i always wondered what causes some people to have a sexual attraction towards their mother
if you're speaking IRL,
i assume it's because of a lack of interractions with the opposite-sex in general and sharing a relationship a bit too-close with one's parent.
basically, if you have no bitches, you will end-up looking at the closest males/females as possible-partners.
now, if you were assuming peoples into incest-porn feels sexual attraction toward their relatives.
no, that's not how it work. there is a lot of walls of separations between theses two-things.
-some peoples jack-off to rape-porn, does that mean they want to rape or be raped IRL? hell no.
-some peoples jack-off to insects porn, does that mean they want to have intercourse with bugs IRL? no.
it's especially different for incest-porn, because it's more of a "theme" than anything else.
a great-man once said "if you mute the sound, incest-porn is just regular porn".
because that's pretty-much it,
take any incest-flick, remove the dialogues, and you have regular porn:
-son and mother action turn into MILF-porn.
-father and daughter action turn into DILF porn.
-brother and sister action turn into regular porn.
-brother and brother action turn into gay porn.
-ect, you can pretty much apply that to every relationships you can think of.
in fact that's how most incest-game devs have been going around patreons incest-guidelines for years now.
you turn the older-woman your character is living with from "mother" to "landlady" and that's it, now it's regular porn.