So let’s say you’re doing something episodic. A webcomic, a series of videos, a chapter-by-chapter fanfiction, a long-running RPG plot, whatever. You ended the last one with something big happening—something large, and irreversible, and of great emotional impact, the consequences of which have been set up and firmly established long since. It’s the next segment, or maybe the segment after, and something’s coming up where what just happened is about to be relevant. Then at least one of the consequences had just been circumvented, with no explanation.
Honestly, if your audience is throwing things at you at this point, I’m not going to blame them. It’s not like this is a retcon; the event still happened, it just isn’t having its logical repercussions—or just as bad, it’s having all the bad repercussions and none of the good ones, and there’s no coherent explanation whatsoever as to why. (This last bit is vital—I’ll get to why in a moment.)
Part of the problem is that it screws with causality. In our genre, there are a lot of natural laws that are somewhat optional, or at the very least circumventable as long as you’re consistent about it—but the thing is, you still want that consistency. In just about any universe, though, actions have consequences, and it’s decently straightforward to predict what kinds of consequences actions have. If things that you’ve made very clear would happen under a given set of circumstances suddenly aren’t happening, you’re going to have a bunch of people loudly asking questions like “Wait a minute, shouldn’t that have destroyed half the universe?” or “Hold it, weren’t these two countries at war last week?”.
Then there’s what happens when there’s attachment involved. When a member of the audience is close to a character—and I don’t just mean a player/PC thing, this happens with straight noninteractive fiction a lot—the last thing they want is for what that character does to be for nothing. If they’re going to make a heroic sacrifice, it had darn well better mean something. When causality leaves the picture, it starts to seem more and more like blatantly jerking around the audience’s emotions for the sake of imagining or watching their reactions, rather than trying to make for an interesting sequence of events.
And before you say this is a case of reader/player/whomever entitlement, I’d like to point you back to one of the early stipulations: there is and probably will be no coherent explanation, particularly if you’re one of those people who has an explanation for everything else. Yes, there’s a decent number of people out there who will get ticked off just because Something Happened to their precious favorite character, but a lot of us are willing to put up with just about anything if we know why, or at least know that at some point we’ll know why it happened, and we’ll be just as likely to call shenanigans if a mess of negative consequences are shrugged off as we are if what’s being lost are positive consequences.
Last, it’s an issue of trust. We go into our stories, our RPG campaigns, our TV shows, whatever, trusting to the author that things will make sense, that we will be able to let ourselves believe in the internal reality so created. This is why, in circumstances that might otherwise seem like this, we often give the benefit of the doubt; we trust that there will be an explanation later, that the internal logic has lost none of its integrity. When we start doubting that, we have to start doubting the overall setup; I don’t know about you, but that’s a point at which I lose a lot of my enjoyment.
Actions have consequences. If something’s been set up to have a certain set of consequences through the entire storyline, and suddenly that’s written off or reversed without so much as an attempt at justification or an offer of an explanation down the line, and there’s no good external reason, it’s not good for the experience. Seriously, don’t.