The game has to appeal to the developer first, or the developer won't be interested enough to continue its development. Any developer trying to develop a game that is going to appeal to everyone will never really please anyone, so he pleases himself and a good chunk of other people that enjoy the game he's developing. This style will also set him apart from the "fuck 'em all, get your penicillin shot at the door" harem games which already have so many offerings from which to choose.
As for the choice of Emily here, the cute, small, feisty redhead has a wide appeal. Another nice appeal of this game is that he went with reasonable body types, not girls with breasts starting at "basketball" and going as far as "weather balloon" that seems to be prevalent in so many of the harem games.
This game is about the story and the "getting the one girl, but maybe having some interesting experiences along the way" not the "it's a frat and sorority orgy with unrealistic body types" "story" which, honestly, almost always lacks in "story" but is only about the sex scenes. That type of AVN will appeal to those without much intellectual horsepower, while this game will appeal more to someone with a few additional IQ points.