It's a Sandbox, so it's not like MC has to sleep with any other girl, when it comes to the ~main girls at least and it's not like (s)he has to get pregnant in the first place. Eventually he'd be able to play (St)Eve's story, date her, fuck her, take her to the prom and call it a day. Whether one takes the pregnancy/threesome option or chooses other girls next to Eve is really up the player.
@rivers77
Nice post, and I totally agree that the game should have more choices, so it enables real "pure routes" and so MC won't have to cheat on let's say Eve to get Grace's content or to finish the main story. Sadly that's very, very controversial and about 50% of the playerbase seems to think exactly the opposite.
I always had the feeling that both DC and Sploosh like these choices though, so I haven't given up hope that eventually we'll at least get some more options here and there.