To bring in the NTR-mechanics easier. That's the only reason this is done. I mean, the idea of "you don't talk to a girl, so she will start to forget you were friends" is working if you don't talk to her for like....2 weeks and it starts. But here they will have forgotten you in 5 days...and of course if you speak to them they will forget you not so fast (every talk = +1 so talk to them 5times a day and you get +/- 0 or just gift them everyday and talk once with them to build up relationship...).
And as much as I like the fact, this game has NTR, I have to say: this system sucks. And more worse, these simply point-based scene showing is also very unsatisfying, especially if you your sister shows you her secret spot every day for the first time, you scare the other, so her milk is spilled...you surprise visit your mother in the shower....EVERY damn day...
This game is promising as hell, but I don't believe this will ever be better than today, because this would mean saddog has to rework so many scenes/flags. But if you look at his update-ratio I would say this won't happen so fast.
Man this game needs a line to follow and which change some of the events. Sisters defloration is one of these things...we don't need her pregnancy, we need memory if her v-card is gone or not (and some reactions of the game to this).
