Compared to other patrols on Wikipedia, file copyright patrolling is severely understaffed, and largely can't handle the number of files uploaded each day. That's why we need the help of AfC and NPP reviewers. A significant number of bad files are uploaded for use on drafts and new articles, so AfC and NPP reviewers are in a perfect position to detect them.
All articles and drafts should be scanned for text copyright violations during review. While checking for text copyright violations, you should also check for file copyright violations.