Completely agree. The whole incest angle kinda put me off at first, but it's so prevalent in these games it's almost impossible to avoid at this point and I've gotten used to it... almost numb to it. Part of it is obviously due to Milfy City's success, but it also just feels like it's being tacked onto games just to appeal to a vocal demographic that apparently can't get off without it. A couple of people have mentioned how they think Philly is a better writer than DPC (and he IS a good writer), but even he has (IMHO) clumsily shoved it into his games. One of the things that really didn't land right to me in one of his games was the whole "why do I suddenly want to fuck my daughter? Weird. Oh well, I guess I'll just go with it!"
It's gotten to be so common that, like you said, it's refreshing and original to have a game without it. Shoe-horning it into a game like BaDIK, especially through a stupid plot twist, would do nothing but hurt the story. I'm glad a hugely popular game like BaDIK remains stubbornly 'vanilla'... it proves it can be done.