Not sure why there's all this disbelief that people would run games without having a destination in mind... It doesn't have to be some kind of radical sandbox for the players to be party to the decision of where things end up.

Do people really not know how to run games like that so much that it's unbelievable that someone could without an impossible amount of effort?

I mean, maybe this is my counter-bias, but I would say well over half of what I play and 100% of what I run, the players (and their characters, and everything about their characters) are party to determining the destination. It's not just the GM. Like, I have no idea how my campaigns are going to end when I start them. I haven't generated the NPCs who are likely to be relevant in the last session by the start of the game in the first. Everything the players do, even if its not intentional on their part, contributes to determining 'what does an ending look like for these people?'.