Perhaps. Milfy City being obviously mother-son and brother-sister incest, perhaps the fact the First person POV MC sex with mom (technically your superior) and sisters (your equals) is less controversial than playing the actual parent having sexual with the child?
That could add a sense of direct pursuit into one's sights, good point.
Extending upon saffe's point, I think there's also a possibility that fathers pursuing daughters is seen as more imbalanced/taboo/wrong than mothers with sons and/or siblings with each other.
Example: as a father with a teen/young adult daughter, I'm constantly being told that there are simple, commonsense things I
shouldn't be doing (e.g., texting any of her friends maybe once a year when a question or birthday arises) because those actions appear improper, while being informed (when I ask) that mothers don't have the same restrictions.