The story that I'm currently working on is in a very far future. Clearly, people will speak a different language then.
Now, I wondered if it can make sense to (partially) create a conlang for the story even though I don't plan to write anything in that language in the final text.
I see two potential advantages of this: First, your language determines to a large part how you think. I guess writing dialogues in the conlang, and then translating into German (the language I'm writing in) might help with the authenticity of the dialogue because the source language character, even though not present any more, still should inform the translation.
Since such effects should be seen also for real languages, maybe someone has already experience (either positive or negative) with the difference between translated dialogue and dialogue directly written in the story language.
The second effect is related, but in a sense opposite: When creating a conlang, at least if you do it seriously, you are forced to consider aspects of the society that you might not think about otherwise.
To explain what I mean with this point, let me describe how the fact that I'm writing in German made me consider questions that I would probably never have considered if I had written in English.
German has two forms of “you”: A formal one (“Sie”) and an informal one (“du”). So when I was writing, I had to decide whether the people in my story should also use both forms. I decided to do so, and that forces me to make more decisions: How close do people have to be to each other in order to use “du” (in German, that changed over time, and it even is different in different social contexts). Also: Is it acceptable to use “du” when you believe that it is appropriate, or do people expect to be asked before being addressed with it? Or maybe you have to explicitly be offered the “du”?
Answering those questions forces me to consider aspects of the fictional society that I might have overlooked if I had written in English where the only way to address someone is “you”. I'd expect to encounter other such aspects when creating a conlang (disclaimer: I haven't done so yet, but watched a few videos on YouTube about conlang creation, and one major element was typically how the fictional culture affects the choices of the language).
On the other hand, creating a conlang is certainly a lot of work. Now some of the work can be omitted if the language is never actually shown (for example, I wouldn't need to give much thought about the sound inventory or the writing system). But maybe someone here has created a conlang for a story (probably in order to actually use it there) and can tell how much it informed the parts of the story not directly using the conlang.
So in summary: Does creating a conlang but not using it actually have the positive effects suggested above, and if so, are those effects large enough to justify the work that goes into creating it?