NTR hentai is for romcom readers a speedrun on character development. Let me ask you: what's more tortuous, having to read more than 24 volumes mainly of filling and repetition or twenty-few pages of equally badly written manga? At least the protagonist doesn't need to reject the other four heroines and end with a half confession and a half kiss. For reasons like this, NTR > romcom & isekai > shounen (both genre & demographic).