There is a reason, I'm done with Electronic Arts and Dragon Age. Not just that, but If you play Star Wars - The Old Republic, it turns out that they made Revan canonically a white, unhinged dude, who married Bastila, while my Revan was a black female, down to earth and Bastila went dark side ( I just find that ending more fitting for someone like Bastila). I hate it, when player decisions aren't respected, including the ones, you put in spoilers. If you don't want something to happen, don't give players the possibility. Problem solved.
I mean the old BG games had similar problems ( and both franchises, DA and BG were BioWare - don't get me wrong, BioWare is great in writing stories, but they backpaddle and recon a lot): If you kill any of the companions, that will appears in BG2, in BG1, they will appear anyway, for example Minsc, Jaheira, Viconia, Imoen. I normally kill Minsc in BG1, because I want Dynaheir in my group and normally don't need Minsc and they only come as a pair, and there he is in BG2, greeting me, like nothing happened.
I really hope, Larian doesn't do that. Given, there is a BG after BG3.
I think you might...
1. Take video games a bit too seriously.
2. Not appreciate the amount of work it would take to continue on stories from every possible ending with every possible action taken. If you want a franchise with sequels to take place and have every action or choice accounted for in every game - then you are going to end up with little to no choices in the games. Or the endings are going to end up being very, very similar as to limit the consequences of choice.
Cyberpunk 2077 would probably be the best example of this. There are like five endings in the game where you end up in different places and you can even end up with an entirely different personality. If they make a sequel where those choices transfer over they either have to pick a canon ending or put in some kind of shallow 30-60 minute prologue where all of those different endings somehow converge so that you can start around the same place. Add onto this if they gave you the ability to just randomly kill any character in the game this would add even more complexity to a sequel trying to carry over those decisions.
I'd love it if all franchise had hyper-complex decisions that spanned multiple games and nothing canon ever had to be chosen as well. But given that there are limited budgets and games actually have to come out in a span of like 3-6 years that is highly unlikely until maybe some crazy new AI/development technology comes out that speeds things up or video games start making significantly more money as to hire even more enormous dev teams.
