This could be difficult because some observations have photos from multiple cameras, and some photos don’t have the information at all.
here are some things I can imagine using such a feature for:
I have two cameras, a “Main” camera, from which I regularly post the photos, and a smaller point and shoot, where I post the observations less regularly. Sometimes I haven’t posted the photos from the point and shoot camera for a while, and I don’t remember which photos I posted last. If I could filter my observations by camera model, it would be easier to find which photos I posted last.
If I am looking to get a new camera, so I can see what kind of results people get using it for the same kind of thing I would.
Because I am curious if other people on iNat use the same camera as I do.