Well, there's an obvious difference between a movie/series/novel/etc. and a sandbox game, right?
In your move/novel/etc. you aren't supposed to choose anything, but to simply follow the story. That's it. In games like SS on the other hand the player is able to pursue the characters he wants and to ignore those, he doesn't. To make that work without glaring gaps or bad outcomes, choices are a massive benefit. Without them it's actually quite hard to write that many different characters in a credible and somewhat interesting way. Especially once there are more than just a handful of characters involved.
I've mentioned Eve's case but you could just as well mention Harold. How on earth are you supposed to decent ending for him, if MC takes his (ex)-wife, girlfiend and daughter? Sure, you could just kill him off or make him some kind of asshole/loser, but I'd much rather prefer the chilled guy he is now either getting his wife back or getting a sweet girlfriend as alternative. It's just a way better plotline.