Because it’s super demeaning when the guy isn’t into it, like is clearly the case here, and the deranged weirdos who’re into it have an annoying tendency to severely downplay that fact.
Point 1: "demeaning when the guy isn't into it"
True.
Point 2: some deranged fans "who’re into it ... severely downplay that"
Also true.
I'm very much into trap/CD, and role reversal (gentle or "bad end"), but some authors put the MC through the vilest sh-t without ever acknowledging it in the comic. You find the same dynamic in gay comics that hit on a straight guy, such as (to pick on a single artist) Isako’s Yakumo to Yusuke, which promptly forgets that Yakumo was completely straight before Yusuke starts asking him out, and never brings up that Yakumo might, for a long-term relationship, prefer a girl.