When you download AI images from Adobe Stock, they aren't saved with "Create PDF Compatible File" checked. That means the thumbnail image in Finder is the AI Icon, requiring users to open files to see what they are. Makes it hard to organize files.
You are correct. Not all (a minority?) of the contributors include that PDF preview. IMHO, adobe should refuse assets like that, as it severely limits the use of the asset, in addition to the nuisance that the preview is not displayed.
ABAMBO | Hard- and Software Engineer | Photographer