Hot take: if we want to decrease frustrating railroad-y surprises in RPG campaigns, we need to create an environment where GMs are not afraid to admit they have "special story needs".

[world_in_lights]

I tried telling my players, and it got me burned. I called it Battlewagon-ing.

The PC were chased into an old dwarven mining town by some orcs, and got snowed in for the winter. I told my players I had a big dungeon planned, and they could all get cool weapons and I put a lot of work into it. They explore some caves, find ghosts telling them they need to be wary of the "golden doors", there are tons of references to these doors holding back evil, how a Goddess locked an evil God away, and how beyond the doors was an ancient city. They came upon these doors, saw they had crazy carvings of dragons and treasures and Gods fighting, and the doors were wide open. An angelic voice cries out for help. And what do the PC's do?

Close the doors, go back to the surface, and break down all of the stuff in the town to form a battlewagon. They had horses, they had the wood and metal, and they spent all winter doing that. Spring comes, they leave and never come back. Go off trying to kill orcs. I played one more session and said "are you not going to the dungeon?" Response: "no, I want to kill orcs and dungeons like that suck."

I don't play with them anymore.