There's a weird syndrome porn games get near the end of the story where they forget they're porn games and decide they're art, and have to make high-minded decisions about which pairings "make sense", or deny the MC the one character they've been romancing the whole game because story, when as players we just.. want to get to the sexy times with the characters we like.
I think that's an oversimplification. Adult games don't always have to be about the sex, they can have good stories that go along with them and the best ones do that, they can make you actually care about the characters as more than just sex objects. They can also provide great latitude in the relationships you can have along the way and the ones you can end up with. The problem, however, is when that latitude doesn't extend as far as you thought it would and can make the eventual ending feel underwhelming and disappointing.
The way I see it, these game are, like most mediums, an escape from reality, but unlike other things like movies, console games, books, etc, there's a greater level of self-insertion where it can make the player can feel like they're living out a fantasy, and I'd be willing to bet that most players prefer games where they can have relationships with multiple women and deal with minimal consequences for it because they would if they could in real life. It doesn't always have to end in a full harem type situation, and for a cast of characters this big it would be ridiculous, but even just ending with certain pairings/groups of characters that the game seemingly teed up would be more than enough.