In a way, once Eric is gone, it becomes a very normal porn game. Where all the ladies are just falling for, well, the beta MC. I mean, MC got expelled from school from harassing a teacher, (not sure if the original BB is the same plot, i forgot), the sisters and mom don't really see him as a man, and yet, if without Eric, they would still go for him. With Eric, there is a reason why the family will look up to MC, if MC proves that Eric is a villian, etc. Not that MC is a saint.
All in all, I feel that Eric creates more challenge, true, I believe people dislike it, due to him able to sleep with the mother immediately, but still, the chances of Mom sleeping with a man that is her superior, and to quote what she says, charming, is more believeable than the Mother hooking up with the MC. Though it is not seen, since the game is on MC's POV, Eric spends alot of time with the Mother, as they work at the same place, when MC is lurking around the house, peeking, Eric is charming the Mother... So yeah....