If you can’t do something smart, what do you do? Something right–at least, when this trope is played straight.
Characters who place honor before reason tend to be idealists, starry-eyed or otherwise. It’s not that they’re stupid–at least, not always–but they do tend to be vulnerable to flaw exploitation. If the Fettered can’t take a third option, this is how he often gets trapped.
On the other hand, without this trope, we wouldn’t have as many heroic sacrifices or men of their word. In the dark, everyone would turn out to be a jerkass, and the world would be a terrible place to live.
Since the best stories often have some sort of moral dilemma at their core, there’s something about this trope that speaks to us, even (or perhaps especially) in the face of sadistic choices and necessary evils. It appeals to the more innocent part of us that still wants to believe in incorruptibility. On the other hand, characters who follow this path don’t tend to think creatively enough to actually solve the problem–or at least, solve the problem without committing the ultimate sacrifice.
Not surprisingly, this trope is a very good indicator of where a story stands on the Sliding Scale of Idealism vs. Cynicism. In idealistic stories, characters who place honor before reason are often vindicated, such as Bilbo in The Hobbit or Luke Skywalker in Star Wars. In more cynical stories, the honorable characters not only get eaten alive, their noble idealism actually makes the problem worse. The classic example of this is Ned Stark from A Game of Thrones, as the cartoon above suggests.
The opposite of this trope, reason before honor, is shoot the dog. Interestingly enough, in the first scene in which Ned Stark appears, he commits an act that arguably fulfills both tropes at the same time (executing a man who is most likely innocent but has been found guilty by the law). Lawful stupid doesn’t necessarily come into play, but it often overlaps. Again, it all goes back to the scale.
This trope pops from time to time in my own writing, though I’m not nearly as cynical about it as George R.R. Martin. Jalil from Desert Stars generally fits this trope, though Tiera is just as honorable and definitely not stupid about it. Stella from Bringing Stella Home fits this trope at first, though her choices are vindicated later on. In Stars of Blood and Glory, though, there’s a character who fits this trope perfectly, and I’m not sure whether he gets vindicated or not. It will be interesting to see what the readers have to say about that.