Well the fact is Larian can do it, but explicitly don't want to do it. It's like asking why there aren't space marines armed with lasers in the game. That's not the game they decided to make.
But ... that's
exactly the game they decided to make! They just don't want certain people playing it.
I have respect for conscious decisions.
I respect conscious decisions too - when they make a damn bit of sense.
Again, here's Swen's reason for denying a party-based option in single-player:
Swen: Yeah, I've heard that quite a few times. In the single player campaign, that's currently not the case. I'm not gonna say “No” - we'll see where we end up with that. But we won't ship it with that option for sure; it would be an enhancement or a modification afterwards. Because I really want people to try out the Origin stories. And if you give [full party creation to them] from the get go, people are perhaps not going to pick the Origin stories; they're going to miss out on all the fun, because they won't realize how deep we went on all of the dialogue options.
So ... he's worried that people might make their own characters instead of picking premade ones with cool stories, you know, because when you make a character for a party you want them to be less interesting.
... Huh? How on earth do those two things correlate? I might as well say no banana splits after 2:30PM - hot fudge sundaes only! - because I'd rather you ride your bicycle than take the train.
If you want to force the player to only use the premade characters, you can simply
force the player to only use premade characters. Why put those character creation tools in in the first place if you don't want people to use them? How come I'm allowed to make my own character for the normal single-player game if that's the "wrong" way to play?
This rationale simply doesn't hold water, and I hope Larian rethinks it sooner rather than later.
