Those would show better than the LIs have lifes outside of the MC.
But why should this be the case at all?
It's one thing in a story to suggest that the MC shouldn't necessarily be THE CHOSEN ONE who gets everything their way, and the goals, aspirations, and life experiences of other characters should be valid as well - meaning the hero might not get the girl (or guy, or whatever) no matter how badly they want them. Bittersweet endings can be just as fulfilling (if not more so) than totally happy ones, after all.
But games are a different animal, especially in cases where a player is given the power to self-insert into the story. Any story that allows player choice at all is by definition implying that the desires of the player supersede those of the main character or the people around them, and the more robust that choice is, the more that expectation exists. The farther the game goes to allow you to shape the main character (by changing their name, appearance, backstory, preferences, etc), the more players may (rightfully) expect the game to make good on those choices.
This is part of why people complained about Telltale games not validating player choice - if no matter what choices you make the story winds up in the same place anyway, why make choices at all? The value of a narrative choice-driven game over a normal book or movie is being able to affect the plot yourself. If you can't affect the plot, why are you playing?
If a dev wants to tell their story and their story alone, why are they making a game? Just write a book or a movie. Making a game with narrative choice comes implicit with the expectation that
player choice matters.
And in that context, player expectation matters. If players want to pursue a specific love interest (
especially in a porn game), then they should be able to do so with the expectation that they are going to succeed. It may require them to make the right choices or perform the right actions, but if they play
well, the payoff should be the reward they desire.
There's an argument to be made that not
every character needs to be pansexual and available to allow the MC to romance everyone they meet (so yes, it's perfectly valid to have a lesbian character who is open right from the start that she's not interested in a male MC), but if the game allows you to pursue a LI option at all it should probably be done with the expectation that it's going to lead to success, not a last-minute rug pull where the person you're romancing suddenly meets someone else and runs off with them instead.
Like it or not, most people play games for some degree of escapism (and power fantasy). And most of us have already lived through awkward social interactions and failed relationships and crushes that never panned out. The last thing the average person wants is to go on a magical fictional adventure and still get dumped and run late on the rent and have to deal with all the other crap they deal with in real life.
You can show that supporting characters have a life outside of the main character in plenty of ways without completely tearing control away from the player. Like it or not, at the end of the day, we are reading a story
about the main character, so yes, most of the supporting cast should revolve around them to some degree. Because the main character is by definition the interesting fulcrum point around which fate and destiny and interesting stories revolve. Otherwise we'd be reading (or playing) a story about those other people instead.
It's the same reason why so many RPGs wind up being about THE CHOSEN ONE who is destined to master magic and fight through armies to save the world rather than about Bob the Farmer who spends 20 years growing crops before getting eaten by a dragon. Because while there are way more Bobs in the world than CHOSEN ONES, most of us don't find Bob's story all that interesting.