An Insight check isn't about how a setting's people, organization, motivations and goals relate to each other, but how the DM wants to give players/PC's that information.
I never said it was. There was a concern that some DMs want players to guess what they are thinking, that players have to ask the "right" question or use whatever the DM decides is the "correct" approach.
I don't do that. If someone asks for an insight check, it simply tells me as a DM that they've been paying close attention to the person they are talking to. Maybe that gives the player some additional information, maybe it doesn't.
For example, let's say Brog doesn't trust people and suspects everyone of lying so he pays close attention. He may notice that Ned is giving signs of deceit or he may notice that while there's no sign of deceit, Ned is frightened. At that point it's up to the player to decide if and how Brog acts on this information.
So I didn't set up this encounter with "The players will discover that Ned is afraid of the syndicate and their protection racket", it's "There's a protection racket in the neighborhood, the body sends a signal to the shopkeepers that they'd better pay up."
Now maybe I decide it makes sense that Ned is the type of person that will be visibly nervous and there's no check required. Maybe I decide he's okay at hiding his emotions and I rely on passive insight. Or maybe I decide that as a merchant, he's good at bluffing people so it's a bit tougher.
In any case, this won't be a dead end if the group doesn't detect or act on his fear, it's just one path they have. If they're successful they get a bit of information more quickly.
They don't have to ask specifically what they are looking for, and I don't plan out "when A happens then B". That's all.