I suspect that the reason for that is that far more fans than creators edit pages on TV Tropes. But yeah, a trope description should indicate reasons why a trope is used.
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman
Lost in Space
Ideally, the narrative role of a trope will be discussed in its description. In practice, it's up to tropers to write it in. It won't happen by osmosis.
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
If this angle has been neglected so far, but is regarded as essential, why not raise more awareness for it?
Also, I advocate for a more formal approach where
- the different "narrative roles" (to be established) have index pages of their own and are more distinguishable from actual trope pages (new name space?)
- E.g. the index for Exposition is already in place. However, Exposition is just one tool to streamline a work, so it seems there is still another layer on top, where Exposition and let's say Distillation (new index for things like Adaptation Distillation, Compressed Adaptation) are grouped together to form Streamline The Plot. I am not an expert, but there seems to be some kind of hierarchy that still wants to be explored.
- there should be another meta index, listing all the main tools a writer has at his disposal. Or is there such a thing already?
- the mentioning of these roles on trope pages should be encouraged.
edited 21st Jul '14 3:28:50 PM by eroock
Lost in Space
I don't consider it "essential" in the sense that you're talking about.
"It's Occam's Shuriken! If the answer is elusive, never rule out ninjas!"
Seems like I got carried away here. 
I've always looked at tropes as being a writers toolbox, and for the most part write examples and descriptions from that perspective. It is almost guaranteed that a writer has to understand story form and function in order to write anything, and the best writers are the ones aware of what tropes they are using and why they are using them.
But on the other hand it doesn't matter how careful you are as a writer, some tropes and accidental/incidental and may not be intended, and the collaborative effort on most works of art mean not everyone is on the same page. On that idea we shouldn't write tropes according to "This is WHY a trope is used" because it is presumptuous to assume all writers are thinking the same thing. The best we can do is offer suggestions as to why a trope is used the way it is.
You have a point there.
I have always felt pointing out why the trope is being used and to what effect is necessary for a really solid example. Without that examples lists always just look like lists of "things that happened (in fiction)" to me.
Feels pretty essential to me. We're talking about always describing what the storytelling purpose of the trope is, right? Yup. Super essential.
If you come across one that doesn't have that explained, it needs to be fixed. Otherwise it is just something that shows up a lot.
The question then becomes "Why does it show up a lot?" There probably is a good reason, unless it is just titillation. Which is a storytelling purpose, I guess, but not a particularly interesting one.
edited 22nd Jul '14 4:14:44 PM by FastEddie
Goal: Clear, Concise and Witty
World's Toughest Milkman
I've long thought that narrative purpose needs to be much more strongly emphasized in the YKTTW guidelines. The closest thing I've seen is the widely-misinterpreted "Chairs".
Speaking words of fandom: let it squee, let it squee.
I feel there is some momentum here. 
What's the next step?
Bringing up and fixing problem pages is the first thing to make in such situations.
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman
For the most part, this site is taking the audience point of view, indulging in the depiction of a trope, its relation to other tropes and finding examples in works.
However, there is another angle which I have come to find intriguing but rarely dealt with on here. The question, why a certain trope is being used and what makes it so effective. This of course not not easy to determine, but if there are authors amongst the crew, it would be great to gather their insight and perhaps turn tv-tropes into a reference book for writers.
This trope has a nicely outlined explanation of why this trope came into being: exposition instead of lengthy demonstration of an attribute. This helps the author to cut down on screentime.
Why is this setup being used? Perhaps for suspense. Whatever it may be, it is hidden within long paragraphs.
Three things I want to raise attention to:
If this has been considered already, I simply missed it.
edited 21st Jul '14 12:19:53 PM by eroock