Writing, anywhere, serves multiple ends.
There's spreading new wisdom. There's sharing your own recent discoveries. There's bearing witness to a phenomenon, or adding one's own voice to support or opposition to it (both of which apply to the Gruber example noted here). There is documenting your own path, hopefully forward. There's simply sharing commonplaces and the quotidian, which whilst not grand or spectacular often serves to record or fill in the details which make up a place or time. (One of my own favourite finds at museums are the incidental details, whether within a larger work or of themselves: everyday elements within a painting, small studies or sketches, archeological artefacts such as the gaming pieces, make-up tools and materials, and sand toilets dating from pharonic Egypt of 5,000 years ago.
I do seek novel discoveries myself, I may have made a small handful. More usually, if I think of something I look to see who might have come across the idea first. If I'm quite lucky, I'm only a few decades behind the vanguard. Generally I see that not as a failure but a sign that I'm treading interesting ground, and not too far from the frontier itself.