I already wrote this earlier:
1. It's already a struggle to overcome without Eric: you need to bend the will of 3 woman at the same time, to accept the idea of an incest harem.
2. There is no struggle with Eric, he comes in the game and starts to fuck mom. You already lost the race to mom, you start with damage control.
3. The bottleneck here is the dev render capacity. So every time the dev makes an Eric scene, he "wastes" time on a unnecessary male, while i think the majority of players want to see nice females.