@Acolytus: Quite the answer avalanche. I also wanted say something. Most has been already told though. I also feel, that it's the trope's fault for being overplayed, that those heros look over cautiousness, naive, even idiotic, but at the same time their characters were heading into a Bad End. It's wise to start planning to avoid that and who says, that there isn't a force of fate trying to counter any deviation from the plot? Maybe a goddess or a villain, that plots against that one character. Just because you are paranoid, that doesn't automatically mean, that
they aren't really out there to get you. 😁
An indication for such a force is, that e.g. many of those characters faced a Bad End, no matter what happened in an interactive visual novels. That's all the reason to act that way and NEVER feel save until the danger (time of the Bad End) has past. They already have unnaturally reincarnated. Anything might jump them around the next corner.
Though...yeah...many MC are just soooo......I really, really do see your point.