When using Dropbox APIs I get media_info=NOT_SET for images even if they are actually visible from web interface

Question

I'm using Python APIs.

When I try getting metadata for one JPG file from a folder, for example using

dbx.files_get_metadata("path/to/image.jpg")

I see the tag media_info=NOT_SET. On the other hand, if I go to the browser and check the file, in the toolbar I see this:

Any idea on why this happens?